These days it's the other way around. If you pirate everything it's all very easy, it's the guessing game and multiplying streaming services where you have to deal with inconvenience. It's all just a little bit of history repeating...
Is it really convenient? Sure! As long as you ignore all the work that goes into setup and maintenance. I’d be deluding myself if I tried to pretend that this is anything but yet another part of a really expensive and time consuming home theater hobby.
Even at it’s best DIY piracy is still miles away from just being able to open up Netflix and start watching.
Of course you can pay for someone else to maintain the Plex server for you, which isn’t a horrible option.
Even a network share would take more work to set up than Plex.
Why Plex? Easy set up, vastly better UI than a network share, works from outside the home. I travel often and frequently benefit from the transcoding feature when dealing with shitty hotel wifi. Friends love it too.
Playing directly from a regular computer isn’t a very good option due to shit format support.
Can you even properly playback 4K HDR content from Linux? I don’t think so.
Format support on desktop platforms is awful.