There is honestly no way something didn't change. I went from being top 5 in 100% of my matches in leaderboards to bottom 5 in 70% of my leaderboards. TDM lobby leaderboards went from a mix of all players to consistently 90% of the lobby being over 1.5k/d, most of the time over 1.7 and it wasn't even parties. I was playing in the day and most people were singles too so it wasn't some bad luck. On top of all that my connections were funky in half my matches.
Of course, they release a mid-day weekend playlist update and after that everything is back to normal but nothing changed with matchmaking. Riiiight.
You have to read the players/connection and make a decision based on that. If you're coming around corners and losing 100% of your 1v1s to vmp/vesper users due to TTK then you have to even the playing field. The TTK for most weapons is close enough where in the majority of situations you'll be able to compete if you have good reaction times, map awareness, etc. so in the grand scheme of things it doesn't matter but once you face someone at a similar skill level to you, that has a connection advantage over you, there is no way you're going to be able to compete with anything but the fast TTK weapons.