That is fucked up, it is not normal or typical in any way, and I’ve never heard anyone else report an experience like this, so I think you either smoked weed that was laced with something much stronger, or you experienced some sort of delirium caused by an underlying neurological issue.
There aren’t any inherent drawbacks of marijuana, but there are drawbacks to excessive use of it, just as there are drawbacks to excessive use of anything. I know people who NEVER stop smoking, they torch bowl after bowl after bowl, all day every day. These individuals, while they are able to function properly, definitely have issues with being absent-minded and having poor short term memory. When I hang out with them I’m always needing to repeat things and their train of thought gets lost easily.
Now, it’s not like they sit staring dumbly into space, they’re mentally “present” and can be very animated and articulate in this state, but, say, they’ll easily forget something that we had planned to do, and have to be reminded multiple times to do something they were supposed to do, or can’t follow the plot of a movie or show. It doesn’t really impede their functioning in a meaningful way, but it can be difficult to stay on topic in a conversation or stick to a goal of accomplishing some activity or other, with these people.
Still, they aren’t even 1% as difficult to deal with as someone who puts away drink after drink all day long.
Edit: some of them have very highly-skilled and high-paying jobs. You have to be making bank to go through as much weed as these dudes do.