Yep, K'sante is still thriving because of his powerful kit.
I think Nafiri is ok, but a very linear and predictable champ. Early game it's not strong and you don't have poke if you play mid. Waveclear for jg is meh and quite squishy, build path is very assassin heavy, but I''d rather play rengar.
Briar was overtuned, but kit is complicated and R is an hit-or-miss skillshot that makes you very volatile against any CC, especially with Rell JG being a good pick, so I guess that's why she's not as popular in soloQ.
Renata, Nilah is also not picked often in soloq, don't see them that much also.
Jax rework was the best thing in-between K'sante and Briar 😂