I've used Plex for years (for free) and, while I'd love it to be free forever with no caveats, I think that making remote streaming a paid feature is ultimately a good decision. They need income to keep the lights on, and I'd rather pay for the service I'm getting than receive a "free" service that comes with invasive advertising or at the cost of privacy.
That said, I have noticed Plex pushing paid content and just because I haven't noticed my privacy being compromised doesn't mean I'm in the clear, so if other people have insight I'd be interested to hear about it before I commit to a subscription.