Correct. Individual MMR is not the ONLY factor in matchmaking by any means, but it certainly factors in (moreso now than before).
Player level is purely based on how much you’ve played, and does not factor into matchmaking as it’s not a reliable indicator of skill.
Operation rank (SR) is similar to MMR but has some of its own rules. It is not used for matchmaking.
Note: Our recent changes affect both MMR and SR calculations. So you may notice the amount of SR you gain/lose from playing ranked matches is different from (and hopefully better than) before.