my opinion, yes, I'm a critic:
Cathedral: Inside could use a lot more work, the walls are bland and straight. The outside didn't look too bad at first, until I noticed roof on the back. It is just flat and looks unfinished.
AK47: Looks good, would have been nice if there were something like an inside, where you could see the bullets, but overall good build. Suspect this is from a model though, looking at the level of the design in this one compared to his other work.
Colosseum: Top row is not finished for no apparent reason at all, also the inside is entirely empty.
White fortress: Circles are... no circles, unless intended, it's not that good.
Travel plane: Aren't these supposed to be round? Also, again, the inside could use more detail. The stair to the roof of the plane... da fuq?
Jet plane: Again, details. The design is totally bland and far too flat for a jet. Also the cockpit area is just empty.
Lamborghini: To be honest, I'm kinda disappointed about this one. Of course the outside looks great, but, this was 100% definitely made from a model. And when you exclude the design and just look at the details he added himself there are some flaws. For example lights, mirrors, engine, doors. All basic parts of a car, and, on this scale definitely possible, so, required.
In short, the builds are not bad, but they need just that little more detail to make it enough. I'd say no for now but don't let him make another build, just let him improve on the current ones.