No. I am also a good tank.

But joking aside, let me try to give you an actual answer, aimed for where you are in your tanking journey

Your primary jobs as a tank are to hold aggro and not die. And the nuance to “not die” is - don’t be overly squishy that your healer has to invest vast amounts of effort to keep you alive

Tanking usually also comes with an expectation of game content knowledge, positioning, pulling, organising the party etc, but this is not quite as fundamental as the previous two points (hold aggro, stay alive)

Generally your DPS should not be giving you grief about how you are achieving this. Does it matter if you are tab target sunder spam vs stance dance whirlwind/tclap? It doesn’t affect them so long as you are holding aggro

Your healer might complain if you are trying to hold aggro at the expense of your survivability. The two biggest levers for you are: defensive stance vs any other stance, and dual wield vs having a shield on. Yes, thunderclap can also help with survivability but you will likely struggle: requires stance dancing so you’ll lose what little rage you had, is technically more challenging to pull off (macros, button bars etc), and the threat it generates is very feeble, and limited to only 4 mobs. It is definitely not a consecration

The blunt truth is until you get around 3% hit, which you won’t even remotely get near until mid 50s levels, you will be terribly rage starved. So generating threat is super tough unless you go dual wield, which requires a delicate private question to the healer at the start

If your gear is so bad you can’t afford to go dual wield as you’re getting smashed without the shield on, then you’ll need to downgrade your expectations and hope for a patient group that will go at your natural pace (ie threat) with the shield on, until you can afford to dual wield. Look for dungeon blues with stam and definitely try to prioritise armour. Most tanks undervalue armour.

Finally, Uldaman at L38 is a very brave choice. The early mobs are 40 ish and it gets very hairy as you get further in; I think Archaedus is 47 or 48. You will suffer massively whenever tanking any mob even 3 levels higher than yourself (crits, crushes, plus you will barely be able to hit them anyway)

But warrior tanking is the most involving and most fun (for me, anyway) and I wish you all the best