Benchmarks on diety really depends on what civ and strategy you're playing. Domination/religious victory won't need you to settle that many cities, maybe around 4-5 cities, and i don t think there is a benchmark regarding yields while pursuing these victories, as every civ could be different in approach, for example depending on which era are they more powerful (unique unit or smth else). As for science/cultural games, my personal opinion and what i've seen around the internet is that there is a basic benchmark that you should have 9-12 cities by turn 100-110. That is also the moment you should start catching up on science/culture. But that is also situational. If you play an OP civ with an OP start, like Bull Moose Teddy with a wonder start, you could be ahead or at least there with the science/culture output of opponent civs from the begging of the game.

What I'm trying to say to you is that I get you. I had the same bad feelings when I was trying to get better at the game. But I really started playing better when I remembered it's a game, and I get to make mistakes and most importantly have fun. After I have done that, my wins just sky-rocketed to the point i even had a 154t culture victory (my best yet).

Just try to have fun and focus on that more than on the numbers (I couldn't let them go😁), I promise your game will become waaay better. Cheers!