To be fair, I think Calyrex (and the two horses) is a mon who is just asking for a movie. It has more of a storyline in the games than just about any mythical before it, at least in recent years. Sure, it's technically classified as a legendary and we don't get movies based around legendaries any more, but there's no reason they can't make one again (and they kind of did with the relatively recent Mewtwo movie). Zoroark, Lucario, and Unown got their own movies and they're just regular mons, not even legendaries.
It really just comes down to "are regular movies profitable any more?" to which I think the answer is perceived as a no, especially considering what a genuine success Detective Pikachu was. Detective Pikachu dwarfed the other movies considerably, and I expect we will get higher-budget and more irregular movies over the prior model of "low-budget movie every year", because it's probably more profitable and better for keeping the brand relevant. Detective Pikachu was an event, the Zarude movie wasn't, even if my 3-year old sister prefers the Zarude movie over Detective Pikachu by a long shot. (Side note her least favourite is the Zoroark movie because she doesn't understand the Illusion concept, which is interesting to me lol).