u mean start playing now?

If you can do at least Abyss Floor 9 & 10, just do it. Can farm up to 300 primogems from those 2 floors alone. Abyss 9 - 12 rewards are repeatable every 2 weeks. Don't sit on it if possible. Go to the main Genshin thread, experienced people can guide you better on how to clear the floors.
Never too late I guess, older players level are capped already. Plus, there's no benefits to catch up with the older players anyway. If you need help, older players can join your world & help you out.

No this is a more focus single player gameplay with multi
Player as bonus.

There no ranking so even start now it's the same you only can't play with your friends that higher levels

Nope, never too late. Probably great too since you'll have much more content to enjoy with the updates and all. It's a pve focused game, so unless you are somehow competitive with your friends and all, there's really not much that you missed out. At most its just freebies from events, but then again, there will be future events too so...

got any questions feel free to post here.. else later do mistakes wasted.. 

genshin impact is more towards single player game, you are not competing with anyone, just play as you like. so start anytime also ok.

if you ask my opinion, if you decide to play genshin impact, remember to join every single events, else you will lose many rewards.