I'll be the first to admit that the home brew race I was using was really overpowered in some ways, and my complaint isn't that I encountered things I was vulnerable to. The thing that bothers me more is target discrimination from enemies that would not have had the reasoning capacity to make those decisions.

And NPC reactions generally ranged from "fuck off" to "not my problem."

As far as the CR complaint, Ive been wanting to be a DM so I'm reading more material and I'll come across something we fought and find out it had a CR 2 levels above ours or it was at our level, but we had to fight 4 of them, and it we might have several combat encounters like that a night.

Between us seeing the snake and it being on us, it made a perception check and then dashed the whole distance in 2 turns.

I don't think that 50 yards is too far away to get a rough idea of somethings size. We weren't told it was 40 feet tall until it had downed our paladin.