I think a lot of new games are driven more around addictive loops than around actual exciting gameplay. Look at Left 4 Dead 2--no addictive progression system, no microtransactions to riddle the game with. The only appeal of Left 4 Dead 2 is its strong gameplay, strong enough to outmatch any other co-op shooter. Compare that to every L4D clone, where content is excluded and the game is balanced to encourage the player to buy microtransactions, and where a part of the appeal is watching numbers go up as players gain experience points, level up, and acquire new toys. In L4D2, you can invite a friend to play for the first time, and they'll have access to all the same toys as an experienced player. In progression-based co-op games, the newbie's just gonna have a worse experience.
Lots of new games essentially feel to me like Cookie Clicker but with extra steps.
Floating health bars and damage counters are another trend I dislike. There are some games where they work well, but usually it feels intrusive and immersion-breaking, and just another way to get players to witness the addictive numbers go up, and usually their presence is a sign that enemies are gonna be absolute bullet sponges.
I'm also gonna say the easy freebie answer, microtransactions have ruined far too many modern games.