A review's not just a review, and that's that: a review has an
angle; a
philosophy; a
purpose.
Is the film good art? Does it approach the sublime? Does it achieve what seems to have been its goals? Will it probably please most viewers? Separately, and maybe very differently, will it probably please its intended audience? Does it seem to have an intended audience, in that you can imagine any group of people it might be intended to appeal to (seems funny, but some films are bad in ways that make it hard to even discern what this might be)? Is the craft itself particularly skillful?
A good reviewer will make it pretty clear—if not in the piece itself, elsewhere that's accessible—which of these is playing into whatever final, concise rating they give, or to the overall tone of the review, and it can be totally valid to base a review in just some of these criteria—in fact, it can be hard to cover all of them in one piece without creating an unreadable, confusing mess, and then someone's still going to demand some boiled-down star rating or whatever at the end, which could mean any number of things and is nearly worthless without context.
There are whole books and courses about how reviews and criticism work, including those intended for a wide non-academic audience, what their purpose is, how to approach them, how to structure them, et c.
Ebert is a great example of a reviewer who largely tried to meet films on their own terms, with the result that, if a movie looked like something you might like, and Ebert gave it even 2 stars, you'd probably like it well enough. If it wasn't normally something you'd like or didn't immediately look appealing... well, you better read the review, even if he gave it 3 stars. That made him an excellent reviewer for a broad audience, but it doesn't mean his approach was the only, or most correct, one (not to downplay how good he was).
[EDIT] Haha, all of which is to convey that I agree with you, and expect and want very different things from a professional reviewer vs. audience reviewers.