It would be pretty easy to accuse this movie of being a tired cash-grab attempting to bank on viewers' nostalgia for a franchise long dormant (specifically, *three decades* dormant). In all fairness, though, Keanu Reeves and Alex Winter *wanted* this movie to happen. Though the resurgence of Keanu's popularity since John Wick took off probably did make it a lot easier to sell this idea to a distributor (hence why we are also getting a Matrix 4... sigh).
The problem with going this long in between sequels is that, naturally, your main actors will have aged. And it's admittedly a bit hard to imagine Keanu returning to his unusually silly role from his youth with Alex Winter in their mid-50's going "Whoa!" and doing air guitar. Fortunately, that does turn out to be the least of this movie's problems; surprisingly, they are able to still make their performances believable as the two crazy rockers while still acting like they have aged.
The first problem with this movie is that it sort of retcons the ending of Bogus Journey (the second movie from 1991). At the end of that movie, it appeared they were very much on their way to fulfilling their destiny, to the point where they were performing *on Mars.* But now... according to this movie... they crashed and burned not long after that, and in fact still haven't fulfilled their destiny or written "the song" that will change everything and unite the world or whatever. Their careers are virtually toast and their marriages are on rocky ground. Oh, and apparently time and space are starting to collapse and the song needs to be written.
Frankly, though, one probably doesn't go to a Bill and Ted movie for a plot. The last two movies at times made about as much sense as Monty Python. With that in mind, I would've just as easily accepted a third movie where some evil villain messed with time to erase Bill and Ted's accomplishments and they had to fix everything by going on another excellent or bogus venture.
And that leads to the next problem with this movie: it feels more serious than its predecessors, and that's not necessarily a good thing. This franchise has been at its best when they've given zero hoots and just done whatever they wanted because it's funny. I would not say that sort of thing often, but even though those previous movies didn't make much sense, it was clear they were not supposed to--and they were so fully invested in the zaniness that it was not a problem. And because of this movie taking itself a little more seriously, this makes the time-travel parts that don't make much more sense more problematic.
Then there is also the ending to contend with. Given that these movies have always have had happy endings, it's not really a spoiler to say that Bill and Ted emerge victorious in the end. But for an ending that would appear to definitively "fulfill their destiny" (since now we're saying the end of Bogus Journey did not do that), it is not the ending that you might expect. On one hand, the resolution appears to at least partially contradict the destinies of Bill and Ted that had been established in previous movies--which is a bit maddening. On the other hand, it does lean on a more on-the-nose interpretation of the metaphor of music being a uniting force that brings us together. This isn't a bad thing by any means, but the issue is the fact that it does not seem to fully jive with what had been built up in the past.
What does still work about this movie? To start with, the two leads' performances. Yeah, it's been 30 years, but Winter and Reeves are clearly enjoying themselves. Winter in particular does a good job of picking up where he left off. And they get to be more creative with their performances when, as in previous movies, they meet future versions of themselves--and this time, thanks in part to improved CGI, the writers were able to be more creative with the possibilities to often amusing effect. There may be less constant humor in this movie than previous ones, but there are still some funny moments (though there's nothing as funny here as the Iron Maiden joke or Death having to say "You sunk my battleship").
Also of note is the addition of Bill and Ted's daughters, Billie and Thea (Bill and Ted named them after the other's friend, respectively--so Billie is Ted's daughter, Thea is Bill's daughter). They're both basically what one would hope for from the offspring of Bill and Ted, and they are welcome additions here. Both actresses--but Brigette Lundy-Paine in particular--do a good job of portraying them.
Face the Music is not without positives, but on the all it's not the (presumed) concluding chapter to this series that it could have been. Despite the best efforts of Reeves and Winter, this one is just not quite able to replicate the spirit of its predecessors. More die-hard fans who want to see these two say "whoa" or "excellent" or "be excellent to each other" one last time will probably want to check it out, but expectations should be a little tempered.