Why can't we see teammates' ping as we used to see back in season 3.

It probably lead to toxicity/flaming/griefing/negative attitudes.

For example I can play just fine in ping levels anywhere from 20-90+

While another user might see anything over 45 ping as unable to play the game properly and they will take it out on a user for simply not having the right coverage in the area/being poorer. Seeing the ping of other players wasn't really necessary- I mean can I ask why you think it should still be a thing? Or are you just asking "Why" without a reason and are genuinely curious?

Because the game is full of snowflakes bumming mommies wifi at 26.

Least I dont see the Hue Hue Hue BR BR BR spam from guys with 700 ping on the NA servers anymore...