I always used old.reddit.com with RES on my desktop. I've started using old.lemmy.world now, and I love the familiarity, but I realize how much I miss RES. I wish there was something for the old.lemmy.world that offered the same enhancements.
The reason reddit enhancement suite existed was because the developers couldn't fix reddit. Lemmy is open source, the frontends are open source. You and anyone else who wants to can fix it.
It still has advantages, you don't have to depend on some server and trust it will keep your data, you can build features on top of a certain front end and don't have to re-implement functionality and maybe even support multiple front ends.
There shouldn't be, but that doesn't mean it cannot be enhanced. Hopefully a popular feature from an extension can become integrated into official web clients.
As a former user of old.reddit.com and RES, I've found the Alexandrite front end (a.Lemmy.world) to be very comfortable. Its not feature-for-feature equivalent to RES, but a lot of the ergonomics are there.
Alexandrite is great. The only thing really keeping Alexandrite from a 10/10 for me is the inability to set the default comment sort to top, new, etc. It’s a minor gripe but having to change it myself every time is frustrating all the same.
It's not all wrapped up in a complete package and definitely won't find equivalents for every feature, but there's some userscripts on !plugins@sh.itjust.works
(Full disclosure, I wrote a simple one to customise the community bar at the top and posted it there)