I have simplified my set up a good amount personally. A lot less customisation on my end to make it easier to manage in the long run.
So first the simple part. I now use LuckyOneUI for just about everything. This a collection addon and profiles that someone else manages and updates. It's still a pretty decent sized list of addons but with the installer getting them all set up is super simple.
So the addons I use with luckyone ui are the following.
ElvUI - Techincally the only required one but I do suggest just getting them all.
LuckyOneUI - Builds off of ElvUI for the main parts of the UI.
Shadow&Light - Another elvui addon that does a lot of little things or does offer layouts of its own if you want to try them.
ProjectAzilroka - Once again this builds off elvui. In this one I do recommend changing the Buttons Per Row setting for the Square Minimap buttons setting to a larger number. Otherwise they go on to more than one line.
AddonsSkins - Just makes somethings look nicer.
OmniCD - All about tracking CD's. Does a lot in partied by default with the luckyone set up but not much for raids. I haven't messed around with it much as the party set up is more than enough for me and I feel it would get out of hand with raids. But you can track things like everyone's CDs, interrupts, and I'm sure other things.
BigWigs Boss Mods - It's bigwigs I think we've convereted most of guild. I believe luckyone does support profile for deadly boss mods as well but I don't use that. If you want it for dungeons don't forget littlewigs and if you want it for old content don't forget all the old expansion ones.
Details Damage Meter - It's details and it's a damage meter that I think almost everyone uses. Luckyone integrates it into the UI with their profile for it though.
WeakAuras - Those that use WeakAuras know how nice it can be. By default this doesn't do anything. Of the the reasons I went with lukcyone is because his weakauras for every class are pretty good as well. Especially since they fit into the UI perfectly. Something to note is there is no healer WeakAuras because the healer layout has raid/party frames where the other weakauras go. You can of course use your own weak auras if you feel you need them as a healer. You can find all the luckyone weakauras on Wago.io including none class specific ones. You can also find them in luckyone settings in game.
Plater Nameplates - The Elvui nameplates are set up in elvui but I like the plater ones more and luckyone provides a profile for it as well. I change two settings in this one from his profile. I general settings I lower the name Overlap distsance so they stay stacked closer together (otherwise they go to like the top of screen pretty quickly) and lower the view dsitance to like 50-60 as otherwise you're screen gets crowded with stuff in different rooms and the like.
With that everything is set up from the Elvui and luckyone installers. I don't really make any other major changes than the ones mentioned. I do change some elvui datatexts but that's personal preference. Like I add the date to minimap one and guild to luckyone bar at the bottom. Oh and I make action bar 5 (right side of the screen one) no longer require mouse over to be seen. I do suggest looking through the LuckyOne Guide on WoW head for installing these to make sure it goes smoothly. The LukcyOne discord is pretty great for support. For easily setting up your keybinds use the "/kb" command ;).
Now moving on beyond luckyone. These are mostly personal preference or things many wouldn't want or need.
AdiBags - It's a bags addon that you can use other addons to make better. There are a lot and bag addons a pretty personal imo. I've loved this one for years. If you use any bag addon I suggest disabling bags in Elvui so its bag/bank window stops popping up as well.
AskMrRobot - My sim tool of choice. Raidbots with warcraft sim is another popular choice. Both offer group discounts if we want to do something as a guild.
Caerdon Wardrobe - A new addition. Great for keeping tracks of what you need for mogs and aslo other things like conduits.
GildenSteuer - Another new addition. I just use it to donate some gold to guild whenever I open the guild bank automatically.
Venture Plan - For making the shadowlands mission table easier to manage. There are other versions like Master plan and War plan for other expansion mission tables.
Maze Helper - Helps with solving mists of tirna scithe maze when you can't rely on group members to help.
Misdirect Helper - Not just for hunters but makes misdirect(or it's equivalents) macro that automatically targets the tank in mythics.
Missing Flight Paths - Not perfect but nice for alts to make sure you're not missing a flight path in the latest expansion. A little bugged with covenant flight paths you can't access though.
Molinari - makes milling and the like easy by just holding alt.
MrFish - Makes fishing and equiping a fishing rod super easy.
Oribos Exchange - Know what stuff is worth on the auction house easily.
Pawn - Quickly see if something is upgrade in theory at a glance.
PersoLootRoll - Makes it easier to know if you want something or to give something away with personal loot.
Ravenous Mounts - Makes random mounts or mounts you can use in specific places easy (like maw before 9.1 or swimming).
World Quest Tabs - Easily see what world quests are available and what their rewards are.
Personally that's everything I have currently. Other types of addons I would suggest depending on your goals though would things like a Satchel addon. There are few different ones but I haven't found one I really like personally. Rare tracking or announcer addons are nice during certian times but I don't care enough to have one. Same with achievement tracking addon or guide addons. If you would like specific suggestions on these I can do so but don't keep up on them enough to know what's still best.
I won't be updating this but I've made a backup of all my addons(addons only nothing else) if someone just want to copy everything I currently have. You can get it on DropBox I guess.