In prior Elder Scrolls games, every character ended up being exactly the same by the end of the game, because you ended up leveling every single skill. Perks make it impossible to truly master every skill, and they ensure that even if you do level every skill to 100, you still won't have a generic character.
But in prior games, every character was not the same in the end because of racial differences and birthsigns. In Oblivion, a female Altmer with the Atronach birthsign would end up quite different than a male Redgaurd with the Warrior birthsign. The Redguard would have his adrenelin rush and a lot more health due to a higher starting Endurance (how much more health depends on how fast each character levels Endurance), plus the Redgaurd will have 75% disease
and poison resistance, while the Altmer would have 250 more magicka plus 50% spell absorbtion, plus 75% disease resistance, plus 25% weakness to fire, frost and shock.
Instead of making the races more different from each other the just made them all the same and eliminated birthsigns. They could have imposing skill and attribute level caps on certain races or imposed skill caps on minor skills or done any of a hundered different things to improve the leveling system from prior games and make characters different from each other throughout the whole game, including the late game.
Instead of doing something original, they just adopted a perk system that has been done to death by other games. If they wanted greater differences between different character builds late in the game, there are better ways to do it than a perks system.