Besides, speechcraft and personality were powerful in Morrowind (speechcraft was OP, in fact).
Considering how potentially gamebreaking so many of the other skills were, Speechcraft wasn't particularly good. The benefits of becoming the master of Speechcraft and, say, Sneak, Acrobatics and Security were not that great when even an average Illusion-Alteration mage could charm anyone, turn invisible, levitate anywhere and open any lock. Still, Speechcraft definitely had its uses.
Well, acrobatics was very useful if you prefered low-contact combat.
Sneak allowed you to bypass or backstab pretty much everything and everyone, and, failing that, it allowed you to pretty much vanish in plain sight.
Security was merely badly balanced, because most locks were too easy and all traps were low level for some reason.
There was definite overlap between security, alteration, mysticism and alchemy, but no single skill from that group made any other redundant. For security to be pointless, you needed both alteration and either alchemy or mysticism (or enchanted stuff).
Besides, there was one neat, athough underutilized use of security - forgery in form of resealing sealed messages.
The worst thing about Oblivion's level scaling was the way it reflected on the gameplay. To make a good character you had to play the game in the most boring way possible, hacking and slashing your way through everything. If you took a bit more interesting route and went with stealth and diplomacy, you'd gimp yourself pretty effectively. Morrowind naturally didn't have this problem.
Indeed, although oblivious had more problems with its skills.
Speechcraft was effectively redundant, because you could boost disposition to reasonable values via wheel-of-derp regardless of skill, and if that didn't suffice (rarely) - everyone accepted bribes.
Security was even more pointless because you could pick any lock at any level without wasting lockpicks (if you knew how and were patient enough to not cut your face with broken DVD at your second lock) AND could get IWIN skeleton key.