The dismissiveness you’re talking about also comes from exactly the same scene and has the same amount of dialogue, so it doesn’t make sense to say that what Mace is expressing is some kind of small outlier.

There isn’t a “vibe” that it’s countering, the “vibe” changes through discussion. Which is the point of having a council. It’s a sequence of events.

Qui Gon reports
They express skepticism at the report
Yoda points out that the dark side is hard to see, so they could be missing something
Recognizing this, Mace gets more serious, refocuses on Naboo but tells Qui Gon and Obi Wan to follow up - he believes there is a Sith involved and this is their chance to figure it out; he also says they’re going to use all their resources on it, whatever that means

What did they use their resources on? We don’t know. What kinds of resources is he alluding to? We don’t know. Why didn’t they send more Jedi? We don’t know, possibly they didn’t want to escalate the Naboo problem. Why don’t they investigate more in the next movie, or between movies? We don’t know, maybe they did but we’re never told. But at the very least we do know that Mace, representing the Jedi council, does believe Qui Gon’s report and take it seriously. Or at least he says that he does.

“Call it a flaw in the movie, if you want,”

That’s what I’m doing. I’m saying the flaw is the script, or the script for Attack of the Clones. It’s not an indication that the Jedi were intended to be suffering from great hubris, at least not in this movie.