They won't bite the hand that feeds them. Take what they say with a mountain of salt.
I enjoyed Marbozir's take. He didn't pull any punches. Probably why we wasn't invited to come play it.
Although on the flipside, if he wasn't invited to play, he doesn't get that extra knowledge and feel. (I haven't seen his full reaction videos yet, to be clear, so I'm not sure his exact takes, or what exactly he's basing his opinions on).
From the various youtuber reviews that were invited to the preview, they gave a LOT more details than what we've seen in the public releases. If you only base your reactions on what you've seen in the gameplay preview, then I can definitely see being very hesitant about things. But seeing the other reaction videos, seeing them talk about the other systems and changes and setups, it sounds a lot more interesting on the whole, IMO.
Of course, obviously those guys got a trip out to visit with the devs, so they're not going to come back with a "this whole release is terrible", at least not until everything is fully out in the open. As mentioned, just the nature to not bite the hand that feeds you. Biffa was very pro-cities skylines 2 in all his preview stuff and leading up to it, but when it came out and flopped on a lot of pieces, then his mentality definitely came a lot more in the "this game needs some serious changes" camp. Sometimes that's an aspect of "it's still early in development - I don't like XXX feature now, but maybe they will clean it up a bit more". And then they don't, or they change it even worse, so now that's another bad aspect.
The good news is that there's still a lot of time before release for them to continue to fix things up. And they have years of future balance patches to continue working. It's definitely not looking like it's just going to be civ 6.5. Arguably this looks like a bigger change in play than we had between civ 4 and civ 5. Hopefully they can stick the landing on it.