besides attunements, if you aren't really accustomed to wow, tbc will be unforgiving to new players, difficulty curve can be challenging compared to vanilla and wotlks easy pve, especially if your on a server with custom values which is likely given tbc devs obsession with making tbc harder than its supposed to be.

also class choice is pretty important in tbc because class balance is not that good early on and inflated values makes it even more apparent. for example if you pick rogue and aren't experienced nor already have a guild to play in, finding a raid spot can be challenging since rogues are abundant but aren't very useful in pve until much later. and when trying to do certain dungeons youll pretty much have to make your own groups all the time because everyone else would rather pick another dps like a lock or a mage or a hybrid with utility.

getting gear or seeing the content can be massively annoying without prior knowledge, and not just as rogue but some other classes as well and if the guild as a whole is inexperienced it can be a bad time.