Musicians

You should consider is record yourself or making your own backing tracks at different tempos. For instance with you saying something to the tune of you trying to do improv and it not sounding good. I'd suggest since you know your major scale and your minor pentatonic then you should say pick a G chord, strum it in time for maybe 5 minutes and record it, then you go back play it and try to improvise over it and only it, simply play your G major (Ionian) and you major pentatonic scales (please not that in G you have the "relative minor" is E, so you can play your Eminor pentatonic and it is the same notes as your G pentatonic.

So record a rhythm of G over and over again, then play only those 2 scales. Think of your own melody over that G chord and try to reproduce in time, then once you get comfortable doing this, then go back and do say a G chord for 8 measures then a C chord for 8 measures over and over again, then work on your lead over paying special attention to the chord change...pretty simple to start, when you have the change coming up, right when you change hit a C note...that's the best way to do it...when you go back to G, make sure you hit a G note. Once you get comfortable with this, then start expanding on your Triad. You should have studied your Triads by now (and inversions) so now you will start seeing that in the case in G major the notes that make up your triad (chord) are G,B and D, so try to use these notes more than others when you are in that chord. The Diminished 7 (in G that would be the note of F#) is really a "grace" note..as in use it to slide or hammer onto G verses trying to use it as a quarter note.

Little things like this take a long time to learn, but it will all come SLOWLY!

Another suggestion and I am sure you have heard it "ear training". You mentioned intervals, well man, say them allowed or hum them in tune. If you go from the root to the 3rd say in G major then you are going G-B....say out loud in tune with the notes and this will help your ear training on your intervals. Also "recognize intervals as other songs". So if you go from the root to the 3rd of the major scale you should hear the 1st two notes of "happy trails to you"...now in the future if you will hear those 2 notes and say "wow that's an interval of a 3rd"

Once you practice this ear and interval training it will stick out about as obvious as a friend calling you, for instance if someone familiar calls you as soon as they start to speak you recognize who they are by their voice.....hearing intervals is just like this. You hear an interval of 2 notes and low and behold you will be able to recognize it just like you would a familiar voice.

I have asked friends that were "good" at playing music how much time to they think once has to put into guitar to become proficient, we've pondered and pondered it and have come to the conclusion that outside of being a true natural then one should expect about 10K hours!

I have an engineering degree was easy as pie to get it, I played college golf, I likewise played a year of college baseball, I was in Nuclear Weapons in the military, I delivered my 3rd kid on my bathroom floor, I started a business from the ground up at age 29 and sold it and retired at 40.........None of these things or "accomplishments" were as hard as learning to be a "real player" of the guitar.