1. Inventory management.
Why it's annoying: It ends up just being "busywork" for the gamer after a fight.Many games also go overboard, purposely giving you tons of weapons which are worthless, instead of just giving gold.
Why it's obsolete: Because inventory doesn't make you richer like it did before. In old games, strong warriors could carry around more loot than weak mages, making inventory a way of making the game different between classes. Now, warriors carry the same as mages as rogues.
2. Turn-based combat
Why it's annoying: if you've ever played Civ, you know that turn-based combat is often clunky and time-consuming. Also, AI rarely is any good at turn-based combat and devising novel strategies.
Why it's obsolete: turn-based combat is a relic from board game days and when you had to actually do like long-division to figure out what happened after a combat roll.
Computers nowadays are infinitely faster for doing combat calculations
3. Click to move. Like you see in Diablo 3.
Why it's annoying: Not as good as WASD movement, you can accidently order your character to move instead of attack.
Why it's obsolete: Click to move was basically a result of tech limitations which forced isometric perspectives for RPG games. Now, you have 3d cameras.
4. Adjusting stats like STR, AGI in games
Why it's annoying: you don't really see much of an effect in the game, and skill trees are better
Why it's obsolete: because modern games have long campaigns. You can find yourself 15 hours in and unable to beat a level because of a choice you made at the start of the game when you didn't know what was going on.