Right yeah, that's why I was asking the question.
In my mind, Hulk is supposed to be the strongest in the Marvel universe because he's limited only by his amount of rage. And while Thor can clearly keep up with him, I don't think Thor has truly fought Hulk at his highest, rage-iest power. I don't think we've even seen that power in his MCU appearances. Hulk's Ragnarok appearance was much calmer and aware that he was fighting for show.
While Professor Hulk is wonderful, I think that is Hulk's, like, base power with no rage multiplier at all. So while he's still technically "Hulk" he's not nearly "the Hulk", if that makes sense. Hulk was clearly confused and scared after his years developing his own persona in Ragnarok, so I don't think we ever saw the real Hulk versus Thanos. And when the Infinity Stones crippled his arm, I think that's entirely due to the lack of any rage multiplier at all. Perhaps his invulnerability/regeneration are also closely tied to that rage he no longer had.
Obviously Captain America shouldn't be nearly as strong as Thanos, but Cap can fight Iron Man to (mostly) a standstill, meaning Stark even in his best suit shouldn't be able to do much either. So Thanos took on Cap, Iron Man and an out of shape Thor that he already beat once before at full strength. I don't think that necessarily belittles Hulk himself by comparison because we have almost nothing with which to directly compare them all.
IMO, Hulk was really underused. I wish Mark Ruffalo's Hulk had gotten a solo movie to really shine.