This is easier said than done, because we never know when a particular project will become inactive. In the past, I had come across a few projects which suddenly became inactive, after a lot of hype and market activity. It is very difficult to differentiate such projects from the genuine ones. Personally I have invested in a few such projects and lost my money. One example that I could give is that of the TMT (Traxia Membership Token). That project was faring really well.. until one day it suddenly crashed at the market.
That's kinda true. There'll always some project that seem really active and after the funding's done then the team will just left the group or become silent to the community. That kind of thing is what pisses me the most they are around just to squeeze the money out of people's wallet and be done with it that's basically the same as exit scam. Also usually when a token is crashing its price as you said the developers will lost their motivation and become somewhat lackeys to their project and that's not a good thing at all.