Every match has a moment where the fight stops making sense to everyone except the one operative who planned for it three rotations ago. That's Rem's whole job description.
You can teach positioning. You can teach itemization. What you can't teach is the read Rem makes half a second before the fight actually starts — the one that turns a 50/50 skirmish into a formality.
Ask around the server and you'll get the same answer in different words: nobody wants Rem on the other team.
Not a breakdown of numbers on tooltips — a breakdown of why the room goes quiet when he locks in.