It's most definitely a choice to not make an effort to learn something new everyday. Education doesn't just happen, you know-- you have to put an effort into it.
Anecdotal reference: I secured an AAS in Criminology and an additional AS in business administration in 5 consecutive semesters. I also obtained several letters of recommendation/merit and certificates of program completions, all in conjunction with my doubled-down majors (albeit on an Associate degree level). It's of importance in this conversation to note that I only remember being sober throughout the 5 semesters for two separate weeks (a week-long event called Riot Week that I attended on two occasions. Fun shit if you don't mind getting shot with baby powder "bullets" and mace while you try and beat the hell out of armed guards that are trying desperately to subdue the riot. There were a bunch of other things as well throughout the week but the actual riot was the best part both years.) Other than that? Smoked out day and night, before class and after.
Upon commencement, I was denied enlistment into the military due to my documented drug use. The CJ degree was foolish of me to pursue and I haven't done a damn thing with it. So, I got a job at Valvoline not knowing shit about cars. 7 months later I was assistant manager. That's hard to do when you can't learn anything, huh? A confrontation with a customer lost me that job (no details, sorry), so I picked up a job at UPS with the hope that I'll be able to put my business degree to use. Turnover rate is ridiculous and I managed to secure a week-long spot at Integrad for driver training so that I can be a cover air driver when the need in my hub arises and I still retain my initial position for when I can't drive. Fuck working on cars, I had to learn a retarded amount of depth of knowledge and DOT regulations/laws just to be qualified to drive a UPS package car.
Now, I say all that not to bore you to death as I'm sure I already have, but to illustrate the fact that if you're not learning things while you smoke weed, it's because you're choosing not to further your own personal education. Weed does not destroy a person's ability to partake in the learning process and you're not only ignorant but a fool because you're willfully so if you choose to believe that weed use means you'll be perpetually ignorant until you stop smoking.