I guess if there is a negative to decouple the positive must out weigh it.
That’s a good way to say it. So many advancements in engineering (and life) are still tradeoffs, but with an overall net gain.
I’m not certain what the best solution might be for your basement with carpet over concrete. My home theater space has tile floors (for now), and my HiFi space has wood floors. In both cases, I felt decoupling the sub and speakers made a big improvement. While one way of describing the the effect of decoupling is that the bass "dropped off noticeably," I would also add that in my experience, the bass still pressurized the room the same and the sound became dramatically more transparent. When coupled, my walls and floor where activated, and the sound was very muddy as a result. While plenty of people in car audio and at concerts seem to want to "feel" the bass, I would argue that lots of resolution and imaging was lost in my case and that the sound became higher quality on net in my rooms. A concrete slab might be different though.