The MMR system won't ever entirely prevent you from being matched with premades unless ZOS changes it to do so or institutes a split queue.

Though higher MMR likely means facing more premades, who tend to also have a higher MMR.

What can you do?

Lose a bunch to drop your MMR?
Play on a different character in a lower MMR?
Beg ZOS to institute a split queue? (IMO, unlikely)
Play with friends/guildies in your own premade?

Yeah, there arent many options, and none of them great.

Roll a new toon and be terrible at it.