Yes and no, but the concept of “difficulty” is a little superfluous for this question.
No: The reason being that you’re at the mercy of RNG. No matter how well you execute your priorities, you can be buttblasted by a string of parries. As the OT, this is much worse, since you don’t get the rage avenue from being hit by whatever you’re tanking.
Yes: DPS is universally higher in Classic compared to Vanilla, and it can be a struggle without Blessing of Salvation on your DPS if they’re geared. In most cases, if we’re not using Salv in dungeons, I will DPS-tank instead, only taunting and focusing on keeping targets off healers, or priority heavy hitters (like bosses). I almost never wear proper mitigation gear, even against most raid bosses. At best, I’ll swap in a couple pieces, barring resistance-centric fights.
If you want your life to be MUCH easier, always tank with a paladin healer. Blessing of Salvation on your DPS, plus fast, instant healing, is the best class you can have to keep you alive. Priests are solid, but shields can be misused and cause more problems than they solve. Resto druids can be dangerous, since they either heal small amounts frequently, or unload massive, but slow heals.
Most of the “skill” in tanking Classic is situational awareness; knowing when to use what ability and where, and gauging your expected rage flow to use your abilities in the most effective and efficient way. It’s hard to convey this in a basic example for a raid environment, but in dungeons you’ll sometimes need to let DPS take aggro. Ideally, it’s another plate, or a mail, but you can generally let casters go. Know which targets need more threat dumped into them, and which targets need very little, so you can optimize your rage/threat expenditure on the right ones. You also need a 1h/shield swap macro to know when you’re about to take heavy damage (this is crucial, being more potent for mitigation than any consumable or even Last Stand will be).
Anyway. For me, tanking with randoms is pretty easy, since I’m very geared, and most of them aren’t. Tanking for my guild is a different story, since they’re geared to the death, and most of our core is competitive and tries to push damage to the absolute limits where they can.