Units I never see (in pro games): is it because they are garbage?

So this is a bit of question I've wondered. I've gotten into playing AoE2 after watching lots of pro tournament games and I was quite curious about the fact that there's lots of units I never see used in pro games, and kinda just wanted to enquire if it's because they're just bad? Or if they're bad in pro games but for us normies are okay (because of differences in micro ability - things like speed of movement and range seem to matter a lot in the pro games)? Or if they just don't often come up because the situations to build them are too awkward?

The obvious one to ask about is UUs. There's so many I never see despite the Civ being fairly popular, and I wonder if that's just because they are difficult to mass because they come out of the castle or because they just aren't worth it cost to effect wise. What comes to mind is:

Throwing Axeman Elephant Archers War Elephants Jaguar Warriors

Less so coming to mind are the Korean UUs (Turtle Ship I'm guessing might be because Koreans aren't seen as a strong water Civ so they don't see use because the Civ doesn't get used). And the sort of unique units, I don't think I ever see the Genitor or Slingers getting used either.

I guess kind of the summing up aspect of this question is: Are pro games and the types of units and strategies they use a fair reflection of the game as a whole? Like at a macro level the pro strategies obviously apply: learning BOs has helped a lot, as well as little tricks like deer pushing - but then my micro is trash, no doubt it'll improve with time and practice but I can't do crossbow dancing whilst juggling an eco and at the same time I wouldn't expect my opponents to be able to do that, or drop quick walls, etc etc.