If you want more jungle variety to be a thing, you need to make invades more costly/less rewarding.

Nothing's going to change with the jungle rosters if it remains trivial to be the stronger 1v1 champ and go invade 24/7 without any fear because by the time laners can collapse on you you've already killed the weaker 1v1 jungler with the current levels of damage.

Either that, or camp catch up xp/gold needs to be put in.

It's going to remain Olaf/Lee Sin/J4/Elise/Rek'sai/Rengar/Ekko town until you fix the fact that much of the jungle is just being the stronger 1v1 champ easily able to bully off camps off the weaker jungler who has no turrets to protect himself with from an unfavorable match up.