Matchmaking needs to stop trying to match you with someone when you declined.

[mapgar86]

Four times in a row, in the span of two minutes, the game tried to match me with someone who had a 6% rating. It's incredibly annoying. After the second time I proposed the match up it needs to learn to stop proposing that match up.

[Jellby]

Or you need to learn how to set karma filters, if you don't want someone with 6%.

[tbhp]

If it stopped trying to match you, that would be like if you decided to red thumb that player to avoid them. Yes, it would be random, not intentional in this case, but it would still be a fairness issue that a certain opponent gets arbitrarily removed from you list of potential opponents.

Edit: I'm talking about Arena here, which might or might not be what OP has in mind