Yep, saw that coming. This kind of plot has been done dozens of times before, it's that cookie-cutter 'I got kicked from my party but hold on, I'm actually OP' story template.
The 'hero' party (lol) called him useless because they don't understand the importance of party composition & cohesion and kicked him out, and only realized after the fact he was the main reason they were successful.
Meanwhile he's found a new partner that understands and appreciates his ability, and he's moving up in the world.
I can see the hero party's hubris dropping them into obscurity and hopefully destruction later from not realizing their own faults and constantly blaming anyone they can for their failures.
I imagine at some point the MC will encounter his former party again after he's long since surpassed them, and naturally they'll berate him and still insist he's useless.
I never really feel any kind of adverse way about the betrayals in these stories, but the one thing that always does bother me is that 'oh and leave your gear behind' line they always end with. Like what? If it was a gift that's one thing, but if he fought for it too (and he did) then they can go fuck themselves.