There is nothing wrong with the format. Most of the sub forums are to do with local stuff and never had loads of posters on them.
The popular sub forums no longer have as many posting IMO because the popular subjects are apparently no longer allowed. "Where is the best pizza in Pattaya" may be relevant to pizza lovers in Pattaya, but not, IMO, to anyone else.
On one subforum, it's basically a small number of posters attacking anyone that has a different opinion that is IMO driving other posters away. About 6 years ago it had a large number of posters contributing, but no longer.
No one wants to post something only to be vilified or abused for it.
If one wants to see why people have left, do an internet search, as they tell it as they experienced it.
Like E-mails and things , technology moves on
If you mean to those horrid not as smart as they think they are phones, some may like that tiny screen, but I never will. Hate them.