Technically, it's true. But here's the thing- for a person who's playing Skyrim for the first time, what's the liklihood of them understanding that you can do this? It's only after the second playthrough and/or communicating with other people do they learn the who, what, and how to bypass these "forced" iniations.
It's forced because you're given absolutly no indication beforehand that you can bypass these questlines entirely, and at least one of them "forces" you to be iniated into one of the factions if you play the main quest as-written and do limited exploration outside of quests. THIS is what people are PO'ed about.
For my first character in every game I usually make choices like I would do if that character were me. So when Brynjolf made me choose, I tried asking around town. Which seemed the logical thing to do. My first direction was the bar because that's where gossip and rumors usually are. Case solved. If you do a little exploring and try things like you would in real life, you find yourself not railroaded.
As for the mages, they even hold our hands at that. If you go to the college, enter by proving you are Dragonborn, you can fully skip the joining quest (talk to MIrabelle, attend the first lesson) because the quest marker will conveniently direct you to Urag. So you can't say that you didn't know what to do since the quest marker itself points you to Urag AND you can talk to Urag without officially joining the College.

"Never done an honest day's work in your life for all that coin you're carrying. Eh, lad?"
I want to to kill him sooooo bad...
You know that if you first meet him while being low on cash, he actually say something like "being low on money, are we?" I can't remember exactly because I always brush him off ASAP

hahaha, I first heard this a few weeks ago when I went straight to Riften right in the beginning because I wanted to pick Marcurio.