Protip: If you don't want to see a movie, don't see it. You'll be much happier not seeing a movie you don't like. Doesn't matter if there will be future MCU projects involving the Thunderbolts, don't watch movies you have no interest in seeing.
I hate this idea of having to watch every MCU movie for the sake of understanding the next one. There is usually a bit of background when new characters are introduced. Monica and Kamala had a brief explanation of their characters in The Marvels. I'm sure Thunderbolts won't be exclusively explained in the Thunderbolts movie. Just enjoy what you enjoy and don't force yourself to enjoy something.
Personally, I want to see Thunderbolts because it looks like a really fun movie with a plot I'd be interested in. Redemption arcs are my favorite. But you don't have to enjoy it.