It doesn't matter if you have 2 Gigabit internet if no one in the world is uploading even half that fast. A single download on Steam is like 450 Mbps
This sounds more like the infrastructure in your area just isn't up to delivering those speeds, regardless what the last mile to the home is.
I promise you Steam's CDN absolutely can deliver more than 450Mbps. It regularly maxes out my 1.5 Gbps at home, and I have no doubt that it could potentially go even faster than that if I had a better connection.
Like plugging a 10Gbps network switch into a 100Mbps gateway, it sounds like a fast final link to the home is being choked out by poor infrastructure in the region and can't be fully utilized.
Street Fighter 6 uses two systems. League Points are a "keep them playing" type, and Master Rate is pretty much pure Elo.
Everyone starts with LP only and initial placement matches put you into a league with progressively fewer guard rails as you live higher. Rookie league can't lose LP at all, there's a win streak bonus up to gold, and you can't demote to a lower league until platinum. Throughout it all there's very slight upward pressure on LP, you get slightly more more a win then you lose for a loss.
Finally you reach the topmost league, Master, the final guard rails fall away and you're given 1500MR to join in the net zero Elo ranking pool. You basically need to demonstrate that you have a willingness to keep playing before they will use that style of matchmaking. "Real" skill based ranking effectively begins there, with the lower ranks being made more to show dedication rather than just ability.