Sorry to do some shameless self-promotion (I think this is OK by RE rules? Will remove if not) but I wrote a freelance piece for Fanbyte about the series, as someone who's been following it since '06:
Eighteen Years in, Ace Attorney Is Stuck in Its Past
This is a history of the series and a discussion on how it seems to have gotten stuck chasing the successes of the first trilogy in response to mixed fan reaction to AA4, and how that's creatively stagnated the series a whole.
Two points a friend pointed out that didn't make it into the article:
1. Apollo Justice is actually the highest-selling game in the series. That Capcom chose to pivot away from it in spite of that suggests they put a
very high value on "not rocking the boat" after seeing mixed fan response.
2. DGS2 had very poor opening sales (as noted in the piece) but critical/fan reaction was very positive. This one was in there previously but got cut during word count.
(You can even put these two points together to ask: will Capcom of 2019 respond to a low-selling, fandom-liked game the same way they responded to a high-selling, fandom-mixed one? I'm inclined to think they care more about sales these days, which is the point I made. But none of this stuff is absolute.)
Anyway, please give it a read, and I appreciate any thoughts or comments!