The concept of Rondo on a bad team is not a hypothetical situation. He was on a poor team at the start and he was on a worse team this past season. In both cases, he did not perform at an all star level. He did not appear to perform better because he was "featured" more.
Rondo's skill set and level of ability is best suited for being on a team of better players. In that situation, his strengths are on display. That seems to me to be pretty clear from the track record. When he is on a lesser team, the effect is that his weaknesses are more exposed. This also seems pretty clear. It you want to argue against what to me is fairly obvious, a counter argument can be crafted. Rondo was young when on the early bad teams. Rondo is not 100% this year and will be way better next season.
So yeah, nothing in sports is absolute but I think especially with Rondo, that the team that surrounds him makes a big difference. More so for him than other players because he has such strong strengths and such weak weaknesses. When the strengths are on display, he can be brilliant but when the weaknesses are exposed, he can be severely limited.