No it's not. I stopped using Plex some years back and switched to jellyfin. Yes it requires more technical know how but it's really not that bad. Plex just kept asking for more money for stuff I thought would be free, so I quit out of frustration. Their buffering times are also longer than Plex was (for me at least)

Plex Pass has two features which I consider to be invaluable. Intro/Credit skip, when an intro or credit sequence is playing a button on screen will pop up allowing you to skip to the end. This even works well with movies with end credit scenes, it will just skip right to them. The other is transcoding, which if you're streaming locally is not really required. Personally, I have dozens of users and some require transcoding because their internet connections are slower than my blu ray rips. Join us at !plex@lemmy.ml

I don't remember exactly, but it used to be that you could only stream to mobile devices if you had Plex Pass (I mean, you could just use the mobile browser instead but that is ofc less convenient). Another perk with Plex Pass is that you can download content from the server to watch offline on your device, for example if you're going traveling. Skipping intros I think is also a premium feature. Possibly the built-in subtitle downloader is also a Pass/premium feature.

But otherwise I don't think it's necessary. Try it out, all the basic features are available in the free version and spinning it up is super easy. If you decide you like it you can just purchase a lifetime Plex Pass.