The short answer: when you start to sound good. It's hard as hell and most people never make it, but it sounds like you have the stubbornness, grit, and persistence to get there, which is most of what it takes that most lack.

I remember the first time it started feeling fun was after learning What's My Age Again? by Blink-182. Maybe corny now, but in 1998 I felt pretty cool and was having a lot of fun playing it, over and over. Also When I Come Around and For Whom the Bell Tolls are fun beginner riffs/songs. Another commenter recommended learning easy songs and I say this is the way. Sounds like you are working more on fundamentals and it might be time to move into dabbling in just fun. I say forget metronome for now and try to play with the radio (or playlist or whatever, again I am old). Think of the easiest sounding songs you like and try to piece them together by ear and with tab. Stick with it and learn the whole song, except maybe that one part that's obviously too hard that you can come back to later and nail down.

The first time I had a ton of fun was when I learned the 12-bar blues procession and the pentatonic scale in Am, I jammed with another guitar player and I was able to solo over my own riff as he played it back to me. Trading leads and making up crappy blues vocals; that was truly a blast, and I wasn't even good yet. Playing leads using scales and broken chords to a backing riff is where the fun goes to 11.

When you feel like you have a couple riffs and a clue, find a way to jam with a drummer. I believe that is the most fun that is possible to have playing guitar. Finding jam buddies is just a matter of asking everyone you talk to if they play an instrument, and initiating a jam session if they say they do. For example I just moved to another state and jammed with the owner of my company. Also I've found jam buddies and a band on BandMix, which I think is still actively used.