Ehhhh, it looks like you're talking about MCU Hulk, and in the MCU, he isn't shown to have that kind of near infinite scaling.

To the contrary, he's shown as having limits multiple times, though they are absurdly high.

Besides, Thanos in the MCU is shown to have the kind of near limitless power needed to match the Hulk, it just isn't in raw strength of muscles. His power is kinda nebulous, but he kills literal gods, including Loki. And, if you'll recall, Hulk bashed Loki around against hard objects without managing to kill Loki in the first avengers movie. Thanos killed Asgardians like they were flies, with no detectable injury.

Now, you could argue that Hulk was holding back so he didn't kill Loki. And that's a possibility, but it isn't canon because it wasn't explicitly said during the movie (and, afaik, by any of the cast & crew afterwards). Since Hulk (and the rest of the avengers as well) was perfectly willing to kill the chitauri during the same movie, it doesn't make sense he would hold back against the entity in charge of them.

So, you have an in-universe example of Hulk not being as powerful as Thanos, even if that limitation is only the willingness to kill.

No because that wouldn't have been convenient to the plot. Don't waste your time analyzing it like this, it's fiction.

Hulk has rarely been treated consistently from one project to the next.

In his Edward Norton movie they went to great pains to show its the heart rate that makes him change, then threw that out the window when he was recast.

We just don't know the rules on this incarnation of the Hulk. We don't know that he will always get stronger.

And I'd have loved to see two entities fly out of Banner-hulk's body when The Ancient One stops him. But we can't have a good Hulk story until the rules are defined and true character growth can happen stemming from that.

Thanos took a punch from Hulk, but beat him because Thanos is a better fighter. Hulk got knocked down, and might have gotten back up but Heimdall sent him to Earth. Maybe angrier Hulk could have been stronger, but we that's not what happened.

To be as generous as possible to the MCU:

Hulk's power has always come from his pain, and Thanos caught him at a time when he had two adopted families (Asguard and the Avengers).

Also, we've seen Hulk lose this matchup in the comics too. His rage is essentially infinite, but so are the resources of the Power, Space, Reality and Soul stones.

Given time for Hulk to get angry enough, Thanos would have lost a fist fight, but Thanos was clever enough not to let that happen.

Edit: And Hulk's decision not to just close the distance and finish Thanos off is arguably mostly down to his own insecurities (both in the comics and the MCU).

It is just ridiculous the wimp they turn the hulk into. He would wipe the floor with anyone trying to have a physical fight with him.

Mcu sucks

Comics are where this would happen

Anger has a limit before your heart gives out