Tanking mythic+ was some of the best fun I have had in this game, especially surviving big pulls on blood DK. I would recommend it to anyone. In contrast, I despised tanking for raids. I can’t put my finger on why.
I enjoyed tanking as a prot paladin in mythic+ but always switched to ret DPS for raids. I think it's because:
1. Mythic dungeons are a little more sandboxy than raids. In dungeons, the trash actually matters, and trash can be interrupted/feared/disoriented/etc unlike a boss, and you have to decide which packs to pull and at what time. You can take different "routes" through a dungeon. The gameplay feels more involved, whereas as a raid tank you just run forward through the linear raid, mindlessly fight trash packs, and most the combat is against bosses who you can't do anything interesting with.
2. In a 5 man group, your contribution is much more noticeable, be it damage, or breaking a party member out of CC, or interrupting/CCing a dangerous enemy just in time, or tossing out a clutch heal, etc.
3. Making mistakes and learning the fight as a tank in mythic+ is much more forgiving than in raids. In M+, if you die and wipe, no biggie, you can just respawn and get back into it and people probably won't start shittalking or leaving. You can have 30+ deaths and still time the dungeon. Even if you go overtime, I've never seen anyone complain and leave. People stick it through to the end unless you're wiping over and over on the last boss like Yazma at the start of Dragonflight season 3. And people often helpfully point out what is going wrong. But if you die or make a mistake in a raid, then people start calling you a shit tank and kick and replace you, and if not, then people start leaving. People have little patience and can't be bothered to actually explain what's going on rather than talk shit. Tanking heroic Antorus PuGs as a Blood DK was pretty miserable, because you'd be doing fine until you get to Aggramar's quadruple hit combo where you had to quickly aim Aggramar back and forth between the raid to soak a swing and away from the raid, and if you screwed up you were immediately replaced and PMed trash.
That's probably why - despite every raid having 10 to 30 players and only need 2 tanks - tanks are far and away the least played role in raiding, when you'd think that tanks would be most in demand for M+ given that every 5 man group needs at least one tank.
EDIT
It is finished.
Signed up at ilevel 440. Had to join and leave the first three groups as it became apparent they were either being led by people who didn't know what they were doing, or inviting anybody who applied including lots of people who were egregiously undergeared (as in people in the 350s, without a note saying they deleted their jewelry). Finally found a serious group, and after forming for 15 minutes we were ready to go. 2 tanks and 18 DPS. No healers because most of the raid is using lifestorm and has leech. We went in and burned down the place until Malkorok, who was the first wall. Attempt after attempt, people did not leave the boss to go soak the purple puddles, causing wipes. After 20 minutes on him we finally downed him and moved on. Smooth sailing until Garrosh (so the raid up until this point took 2 hours 30 minutes), who we got stuck on for an hour and a half. First issue was people weren't leaving Garrosh to go kill the engineers who hurl the Iron Stars. Then people needed to stack. Towards the end we took off, unsocketed our prismatic gems, and deleted our jewelry to drop our ilevel below 370, which dropped Garrosh's HP from 7 billion to 1.9 billion, which was very nice. And then once people stacked together we got the kill.
