Agreed, there's a big increase in trans porn, trans OF pages and more trans escorts. There are also more strip clubs that have trans dancers or nights or are exclusively trans strip clubs different than the old drag type clubs. I don't believe onlyfans and other personal adult pay sites have peaked in growth yet based on the metrics, some categories may have slowed in growth but not close to decreasing yet. The metrics support the notion that the oldest profession in the world isn't decreasing, it's still growing with the population.
The difference with reviews being down seems to be more a change in how people see the risk vs reward. Meaning, they'd rather risk losing several hundred dollars than being caught for prostitution and worse their wives and families find out they're engaging in it because they used a site like Ashley Madison who "accidentally" shared their personal info. Or they're don't mind getting caught for prostitution but don't want it known that they seek trans escorts?
I also find more providers these days don't care if your going to review them or not. For a while it was a way to get them to take you a bit more seriously, perhaps give better service. It often means nothing to most providers, review me or not, good or bad it doesn't affect me, I don't care. Today many providers change their name, number and location several times through their time escorting with all the avenues online today it's easy for them to do.
I believe these are the 3 main reasons reviews are down overall; 1) more ways to make money in the adult/sex industry but not exactly escorting; personal pay sites, video chat, selling pics and clips etc. 2) Potential clients more worried about their personal info being shared or stolen. 3) The anonymity the internet brings to the table for people to change their name, number, location and so on today vs 15-20+ years ago.