This is true to an extent, until you grow out of that. I won't argue that pot makes music more vivd when you're younger or less experienced. This is true.
But after the initial "turned on" curve, your ability to rapidly progress on the instrument declines, for a variety of reasons. Your ability to "jam," or more precisely, feel good about what you're doing increases, but your complexity of ideas and your advancement and retention of idiosynchratic musical methods does not. This is a topic very near to my heart, and I think about it constantly.
Not to mention it's a bitch to play two sets while high. You have to keep smoking or do speed or something. You go backstage at setbreak, blaze, come out all geeked, and you rock the first four songs super hard...and then you start to rapidly lose steam. And your higher register notes of your voice start sucking...
Ever wonder why great "jam bands" start sucking ass as the years go by? Don't people normally get better with practice?
Isn't there a part of you that says, if I need to do a drug to enjoy doing something, maybe I'm not really cut out for it? You know, there is such a thing as a true artist. The time-worn stereotype of the druggie-musician is as valid as saying all black men play basketball.
And sometimes feeling good for no reason is a bad thing. Sometimes being "cool" with certain people is a bad thing. I love Dave Chappel's line about why he stopped smoking weed--he was gettin' high with the KKK.
And sorry, Keith Richards bangs a few chords on a five-stringed Telecaster. You may like his music, but if that's as good as I got after decades of playing, I'd just OD and get it over with.
I took a permanent break from dope, moved to the middle of nowhere, and practiced guitar non-stop. In one-year I went from a decent college-town player to a full-time professional player in a large city. I am 100% sure this wouldn't have happened if I was still smoking daily (and growing

). There just isn't enough time to fit
real practicing in with heavy partying and the social life that goes with it, the amotivational syndrome, etc. Can you get good while smoking? Sure. Can you lift weights while being a stoner? Of course. But I don't think you'll ever reach the upper echelon unless things like getting high are your absolute last priority, if even on the map.
Music is so much more of a high when you don't need to get ripped to be amazing. To be totally straight and feel like an electric cable is plugged into your spine when you close your eyes and take a solo is amazing, and its free if you work for it.
It's like the difference between doing acid to have a "spiritual experience," versus being truly enlightened 24x7. After a while you get tired of looking over the fence at something that looks cool, but you can't take back with you...and so you figure out how to grab what it is that turns you on naturally.
I have yet to see someone I respect who smoked a good amount of pot daily for decades and didn't have a host of issues I would rather not have. And on the flip side, everyone I know who doesn't smoke has a much more varied persona, many more dimensions, interests, etc. Think about it--if getting high truly made people better at things, then the very top in every field would be major stoners: If you asked a theoretical physicist how he came up with Superstring theory, he'd say, "Wicked dank nugs, bra." Instead he speaks fluently in a language everyone is free to learn, yet most would consider foreign. If you asked a physician how he was able to sever the corpus collusum of a patient with severe epilepsy without killing him/her, he'd say "Northern Lights Number 5 and a four-foot phatty bubbler." Instead he rapidly exhausts the normal person's attention span with an explanation of his theories and their applications.
Its a drug that alters your perceptions. It's not a smart drug. It's an empathogen to a degree. But it doesn't increase performance. Steroids increase performance. Speed increases performance. Better sleep increases performance.
Oh, one other thing. I believe very strongly in situation-specific memory, and I use this to explain why you remember some things only when you're high, and also why test-takers usually suck when stoned, and why classroom retention is lower when you're high. In other words, marijuana doesn't destroy your memory, it just puts it in the "stoned" memory file cabinet, which remains locked until blazing re-occurs. This also is in line with the brain cell research...marijuana seems to leave a "film" of fatty-type deposits on your brain. I have seen many photos.
BTW, high school sucks. Everyone worries so much about what everyone else is doing...people get in your shit for no reason...no one is responsible for their rent, bills, etc., but most are "adults" by law. If you're smart people hate on you.
In the end I do agree that pot is less harmful in the end than alcohol. But having to chose one or the other is a false dilemma. Sell the weed, buy a good metronome and a good instructional book, and practice the shit out of your instrument of choice. Or lift like a banshee.