For both classes you had a lot less than 8 slots for a long time. Call them "memorized" or "slots" but the point is there were only so many spells you could activate at a time. Worse, you could only activate each of those 8 spells one time per day so your total spell load in any dungeon in DAI is unlimited casting, in BG it was X based on your level. You have a staff in DAI and it casts a spell for you, unlike BG2 where you used a staff occasional to throw ice bolts but used a sling for most of the game
Warriors didn't get an 8th bonus feat until what 15th level and a lot of those are what we would now call passives - the weapon focus stuff for example. Rogues had a fixed set of skills and again, a lot of those would be called a passive type ability.
Limits on abilities aren't anything new and they don't ruin "the point" of any game as if the point of a game is to cast spells as an end into and of itself. People need to learn to let the game be the game. BG looks nothing like DAO which looks nothing like Skyrim which looks nothing like KOTOR which looks nothing like Fallout which looks nothing like The Witcher. Every game has the quirks about it some things you like, some aren't the best but the hyperbole is unreal.
I never said it ruined the game. I said its a poorly conceived design choice. If that is all you can think of to limit the player's effectiveness against your creatures then you've severely limited your ability to challenge anyone.
That may be how you played DnD, I'm a min/maxer and I can get 8 spells by level 3 with over 30-40 selections including much more diverse spells. Not just fire, elec, cold or shield. Sleep, illusion, hold person, spiritual hammer. Then you add scrolls, wands with 50 charges a piece. Look I don't want to get into another game here, but sufficed to say you are wrong. By level 27 I could do damn near anything I wanted in those games, where as here you are still limited to 8 slots and 16 or so spells.
DAO was awesome, you had tons of spells. I would absolutely love it if the selection, choice and tactics were in DAI. They are not, DAI is just shallow and repetitive. It's cool if you disagree that its shallow or repetitive, but the truth and facts are that its much more limiting and there is no substantial reason for it other than, cause we said so.