Level 62 cloth wearing mage here.
I get my ass destroyed if I stumble into a fight like an idiot. Tactics are essential.
Unlike a lot of mages I didn't invest all of my points in magicka, so I don't die instantly unless I get hit by a daedric arrow from an ebony bow... which is frequent at level 62

If I use dragonhide and a fortify health before a battle then not even arrows come close to 1-hitting me, can take 3+, same as a heavy armor warrior without a shield.
Illusion and Alteration just keep getting more overpowered as you level up.
Destruction stays powerful enough. When you just need to kill things extremely fast you can chug a fortify destruction potion, or even higher with both a potion and a poison. I took down Alduin at level 62 in like 5 seconds this way.
Mages are only inferior if you think planning and preparation are too inconvenient for you. Just keep in mind that a lot of the difficulty complaints are coming from melee characters that many mages aren't having problems with.