You say that as though it is a fact, when in actuality, it is not.
I, for one, believe we have more choice than we did before.
Attributes
-I don't see this as a loss at all. Everything that Attributes covered is still in the game, either through the Health / Magicka / Stamina bars (which is really all that most attributes in past games covered anyways), and what's not covered in the 3 Attributes we do have is covered in perks (I.E.: staggering, damage, carry capacity, etc.) The only thing that's not in Skyrim from past games is Speed, and that is actually done in a different way with sprinting, which while not the same is really just a different way of accomplishing the same thing.
Which is ultimately the difference between how Skyrim handles it vs. Morrowind or Oblivion. The results are still there, they haven't been removed, they are just handled differently.
You don't like the way it is handled now - which is a totally valid opinion - but it is a subjective one. Claiming that it is not there is an inaccurate statement of fact.
Birthsigns
-Again, the effects of the Birthsigns are still in the game, they are just now handled differently in the form of Standing Stones. Again, you don't like the new way of doing it compared to the old, but it is a subjective preference, not a factual lack of content or "RPG mechanics"
Classes
-Actually, classes are just the same as before, the only thing missing is the label.
In Morrowind or Oblivion, you pre select a handful of skills that "define" your class, and as such you level up, but there is nothing that limits you to those chosen skills. You are still able to branch out and become any kind of combination of skills you want, including becoming a full fledged master of all. You level up by doing, and there is nothing in game that stops you from branching outside of your "class" except yourself. "Class" was just an arbitrary title that had no impact on the game whatsoever.
Fast forward to Skyrim, where skills level you up by doing, just like past games, and you can focus on any combination of skills you choose, just like past games. The difference is that where in past games, you "defined" yourself pre-game by tagging some skills and giving them a label, in Skyrim you instead define your class as you play by investing perk points in the skills and perks that would define your character.
As such, Skyrim actually has more of a "class" system, by restricting you more, as you cannot fully perk out every skill, so unlike Morrowind or Oblivion, you actually have to make choices about what skills and abilities will define your character.
I don't agree here. One of the big problems was that there weren't enough differences between builds to make it worth the loss of atributes and classes. You do make choices in the perks, but not really restrictions. I think the brilliance of an RPG is defined by what you can't do as much as what you can do. In Oblivion, if I started as a pure mage, I wasn't going to be tearing off limbs with axes. If I was a sneaky theif, odds were that I wasn't gong to be able to be a great spellcaster or a great mage. Having a good startting sword skill meant that I wasn't going to easily pick up an axe. It goes down to the idea that the person who can do anything is not that good at anything.
Meaningful Difference Between Races
-There really isn't any less difference in races than before. If I want to be a magic class, I will likely still play a Breton or High Elf, due to their magical bonuses and extra spells to start off with, if I want to be a warrior class I will still likely play an Orc or a Redguard with their bonuses to combat skills, and Khajiit and Wood Elves still make the best stealth characters because of their bonuses. Every race being able to excell at every style is a trait that is shared in both Morrowind and Oblivion, there is no more "meaningful" difference between the races in past games than there is in Skyrim.
Not really. With attributes, you had Altemer who were great mages and terrible warriors. Orcs weren't good at anything other than fighting. Khajiit made good sneaks. Imperials were good at a lot of stuff. I never saw the same in Skyrim -- any race can do anything.
Less Player Choices
-I would argue that we have more choice. When developing your character, you actually have to make decisions on what skills and abilities define your character, because you can't fully perk everything, where as in Morrowind and Oblivion, there was no significant choice save for what skills you wanted to define your arbitrary class tag. But you could still fully branch out and do anything and everything in terms of skills, which meant there was no real choice. Perks in Skyrim allow you to specialize your character in ways never before seen in an Elder Scrolls game. As far as quests go, Morrowind and Oblivion were particularly linear as well, but Skyrim actually offers aspects of choice in its quests, whether it's with Paarthurnax and the Blades, the negotiations between the Stormcloaks and Imperial Legion, how to deal with Saadia, how to figure out the truth behind "A Night To Remember", or any other number of questlines with choice.
I like being able to define my "class", and perks are cool. My compliant with the "lack of choice" is that doing or not doing a quest was about the limits of "choice". And even those few that allow you to decide HOW to solve the quest, the consequences were by-and-large nonexistant. If you betray someone who trust you, they won't care. If you shake down a shop, the barkeep will still ask you to help him make a very valuable matrimonial ring. If you side with the stormcloaks, killing them doesn't affect your standing with them (compared to Oblivion where robbing your guildmates meant being kicked out and gathering herbs until you'd done enough penance). Even joining a guild is a causual affair. The guilds don't care what other guilds you're in. Join everything, no one cares. No one will look down on you for being DB, no one will care that you are DB, TG, Companions, and College of Winterhold. Didn't matter what you did -- it causes no greater constrenation then my choice of steel plate armour.
Less Diversity
-I would argue this as well. In Morrowind, a very large percentage of NPC's you encountered were Dunmer natives of Morrowind that didn't like outsiders. It is no different than the Nords in Skyrim. While Morrowind NPC's had repetitive recycled text dialogue, each voice acted NPC in Skyrim has some kind of unique story or tale to tell. I am much more invested in the NPC's in Skyrim than I ever was in Morrowind. As far as guilds, I feel there is plenty of diversity, where the College of Winterhold is completely different from the Companions, whereas in Morrowind, they were pretty much the same thing outside of the fact that one group did combat and the other group did magic.
Well, true enough, but the "unique" stories aren't even all that unique. There's a vegtable lady, and her kid who helps sell vegetables at her stand, and that's all that there is. Or the Redguard who kisses butt and lives in Cloud District and tells you at every opportunity. They don't have the same kinds of background as even Oblivion. I still love Mahei and his wife hiding from each other, or Mazoga who acts tough and then becomes your buddy. Or the Skooma Den. It's not that there aren't somewhat unique, just that the personalities are so muted that they seem less than interesting.