I recently watched a video from Preach about returning WoW players. His co-worker had started playing War Within and already quit. The reason he/she quite was out of frustration of basically one/2 shotting everything. You can’t learn how to play when everything dies faster than mobs do in Diablo 4. People might say “You can take off your gear to be weaker”, well, yes, but then you don’t actually get to feel how the character plays. The character is going to feel like garbage because I am wearing half the gear I should be just so monsters don’t instat die.
Well, I am also a returning player I haven’t played since Shadowlands. I have to agree with this co-worker of Preach. I can pull entire screens at level 55+ and everything dies in seconds. I normally one shot most monsters more often than not. Like I said, things die quicker than they did in D4.
It’s hard enough trying to figure out what does what now that the UI and Talent trees are very different, but now I can’t even figure out what does what because everything dies before I can tell what’s going on. This leaves me forced to use a target dummy and while I am standing in a capital city I am not exploring the game and seeing the world which is suppose to pull me back in.
So you need to either make using a Target dummy more amazing than actually questing or give those monsters higher defenses or HP so they literally don’t insta die.
Perhaps a “Returning player Tutorial” which I would have appreciated, since the UI is so very different 5 days now and I’m still can’t find everything. They use to have that training hall / Proving Grounds, but I heard it got removed, which is a real travesty I actually liked that thing and used it on multiple characters. But having something like that but an expanded tutorial or maybe a Tutorial that’s made from a Delve? Something is better than nothing.
Wlcome back!
Is it really THAT bad now? I haven’t looked at low levels since launch.
Talents have changed quite a lot, yes. For a quick start, look up your recommended talents at icyveins.com
UI hasn’t really changed that much … uh, ever. Were you using an addon/UI pack before that you don’t have now? Curseforge.com will set you up with addons.
Proving Grounds is not gone. You can fly to Temple of the White Tiger in Pandaria and walk right in, and request a session. Or your Garrison mission keeper will offer you a teleport into the instance.
Once you hit 60, you will qualify for Follower Dungeons.
Open your Dungeon Finder, choose Follower Dungeon from the dropdown, pick a dungeon. You will be ported there with a team of 4 NPCs to complete a dungeon. It really is very good for practice - even better than Proving Grounds. On the one hand, it’s a genuine dungeon, with all the mechanics and trimmings, and on the other you can stop as much as you like to adjust your talents and UI; the NPCs don’t mind waiting for you. 
Oh the UI has changed a lot. The UI not only refers to what’s on your screen but also all the hidden options such as sound, graphics, key binds, ETC. Ya know mounts use to be carried in our bags, so the UI is very different than what it use to be.
They rearranged my key binds. Some are what they were, some are not, such as I always use to have 4 bars, and now just two, but when I found where they had them and turned them back on all my keybinds I use to have on those bars were gone. I’d say the UI is about 30% or more different than it was when I left. For instance the leveling tree, they let you go back to changing specs again like it use to be. There is a lot of things they fixed and reverted Legion changes, BFA, and Shadowlands changes back to WoD or earlier. Lots of good changes, I just feel very lost. The builds are so different I have been just running around in the Dragon Isles trying to get a feel for how the game plays again, but as I said everything dies so fast… I tired different classes and I’m like… “Oh boy this is going to take a while to figure out which class I like most with how easy everything is to kill”.
But ya, I totally nuke most things, I my lava lash alone most of the time one shots what ever I’m hitting.
Oh, and can Icy veins now be trusted? When I quit no one used Icy Veins for years it was so bad. I think Wow head is what people used. Though I have noticed a clear lack of information now that it seems the player pop has dropped drastically since Shadowlands. But I’m hoping War Within will see a turn around. I’ve been pretty happen to see a lot of the changes I have so far. It does feel a lot more like at least like MoP which is still not WotLK, but it’s a good start.
Icy Veins was never that bad. There was another site, Noxxic, that once was quite good - up to Cata, I think - but then fell off into uselessness. Maybe you’re thinking of that. Ion once made a remark about players going to Icy Veins and getting confused, or going to Noxxic and getting misinformed.
IV is certainly more than fine for levelling and pre-raid. After that, if you are looking to min-max, you will get picky and check them all out - IV, Wowhead, the Class Discord. In all cases, the recommendations are made by some specific player; the quality depends on that player, not the site. Then retune for different bosses/M+ dungeons.
I don’t think the Retail player pop has dropped since SL. It did drop through SL, after CN, but picked up again in DF. Recently, the owner of WarcraftLogs says he thinks WoW overall has the highest player numbers ever - but now spread across Chinese Wrath, Classic Cata and SoD, and TWW.
Give it a week or two and Bellular and Preach will be doing somewhat unclear vids on the raiding numbers, comparing SL, DF and TWW, and we’ll either know for syre or be even more confused, but on a higher level. 
At any rate, get to 60 or 61, or choose Dragonflight at Chromie in Org outside the Embassy, try out the Follower dungeons, and then just queue for some regular dungeons. You’ll be on your way before you know it!