What else they could have released this month, if they didn't make Thunderbolts movie? A sequel for BP3, DS2, Shang-Chi and X-Men reboot?
X-men is currently in development, and who knows what state the X-men reboot would have been right now, if they didn't decide to make movies for Eternals, Black Widow, Sam Wilson and Thunderbolts* first. Those movies being released first, are indeed factors why they haven't made a X-Men movie, because these Ips are under 1 company and Marvel Studios was/is preoccupied with other things, hence why we are still waiting for an actual reboot. Those movies won't affect X-Men if they aren't under the same company. They are since the Fox buyout was finalized.
As for Thunderbolts doing much better at the box office if it was released when they were peaking, well duh. I've said that in the past as well. But their lack of hindsight post Endgame is why they are no longer at their peak. Deadpool & Wolverine still earned more than a billion because thats something people wanted to see which I can't say to Thunderbolts.