Some good responses. Mine will have some repeats and something new to this thread.
I do not miss
-Longer load times. HDDs and optical drives are quite slow compared to SSDs and Game Cards. Cartridges were thankfully fast mostly back in the day.
-Proprietary memory cards. There are memory price issues right now, for sure. But at least for most of the systems you have more of a choice.
-Less international releases and content
-Gimmicks for controllers and hardware that were often not used well.
-Slow download and install times
-Lack of timekeeping for a lot of gaming history. I like that the eighth generation onward kept track of how long you're playing games. And Steam started showing it in 2009.
-Lot of games that dipped below 30 FPS, and some that could really never even hit 30 FPS.

I don’t miss external memory cards, and I certainly don’t miss the complete inability to save. But I’d welcome the return of memory cards if instruction manuals made a comeback.

I don't miss the often obnoxious and cheap difficulty in a lot of older games, which usually felt like a way of just prolonging the experience instead of a fair challenge.

Also don't miss having to start a whole world/chapter/etc all over again from the beginning if I died too many times.

You kinda just explained rougelikes...

Which I why is generally fucking HATE that genre lmao

Me too. There are a few exceptions like The Binding Of Isaac, Dead Cells, Balatro and a few others, but as soon as I see the word "Roguelike" on the description of a game, I lose all interest most of the times.

Chiming in, I'll give roguelikes a chance occasionally. I suck at them, but I like the few hours of spent with The Binding of Isaac.

But yeah, that explains why I don't usually like NES games, old arcade games, and such. 

Games without saves, limited continues or such as the default for said game (no options to adjust it) are thankfully mostly gone nowadays. 

Loading times.

I love older games. At least from the 3rd gen and up. I guess I give them more of a "pass" because they are older and the developers had more limitations they had to deal with compared to developers of today. They can still be frustrating as all hell though.lol

Wired controllers.

Every big game releasing in the holiday season so Spring and summer months are mostly dry. 

3rd party controllers being shit. These days we have 8bitdo and such doing great work.

Memory cards. 

Screen tearing in the 7th gen. 

Racism/bias against Japan in the 2000s but mostly 7th gen. 

Any E3 shows 7th gen and up to its death. Miserable.

Worse accessibility.