I'll even expand on this
1. Skills. The 1-100 skill system in Morrowind and Oblivion sucked. It spread power gains out over such a large range that you could go up 20 points before noticing any actual difference. Skills were merged down into 5 +20% perks, because it made power gains more noticeable, and cut out all the flak that did nothing from the 1-100 skill system, while still offering the same, and in some cases greater, power gains.
2. The 1-100 attribute system in Morrowind/Oblivion was equally as bad as the skill system for many of the same reasons. To make matters worse, since skills and attributes overlapped on what things they improved, it meant the devs had to split the total power gain across both, further reducing already low gains into basically nothing. By merging the attributes into the skills they modified, and just letting us boost HP/MAgicka/Stamina directly per level, they increased the power gains we get, and allowed for far greater ranges of HP/Mag/Stam then before, increasing effective character diversity.
3. Classes were simply pointless, as, no matter which class you took, you could still do whatever you want, join all the guilds, and raise all skills/attributes to 100.
4. Birthsigns had many of the same problems traits did in Fallout. In that some of them were so bad they could make the game neigh unwinnable, most of them were so mediocre there was no point in taking them, and then there were 2-3 so good there was no reason to not take them.
To compound the issue was the first you had to pick a birthsign before the game started, and thus, before you knew how the game played, or what the birthsign would do. Which just encouraged metagaming, and restarting the intro of the game 20 times till you found the not shit ones.
By making them into other powers/standing stones, Bethesda kept the same functionality as birthsigns, but did so in a way that was a lot more dynamic, and a lot less needlessly detrimental to the game.
