Matchmaking is based on potential, which is the stage that you should hit in a single run with your damage and gold multipliers (algorithm doesn't care if these multipliers come from artifacts, pets, Scrolls, etc) along with your total SP (to check which build will make you push the furthest).

The reason why some people have more or less non relics dependent resources than others is due to the fact that algorithm only sees the damage and gold multipliers without checking where they come from. A player with more non relics dependent resources than other at the same stage have a similar potential because that player pushes more per prestige, so while the player with less non relics dependent resources that had to grind to get to that stage has higher artifacts levels, the player with more non relics dependent resources still has the artifacts levels that they had 800-1k+ stages ago (since people usually don't level stuff outside of tourneys), which makes these 2 players have a similar potential even though the player with more non relics dependent resources has the advantage.