Can more than understand! It's a bit harsh of a criticism as I have gotten to the point that I can compose music really really fast (been doing it for 7+ years now) that I am happy with.
But the thing is I find it hard to balance whether to rate games with custom audio/music made during the jam higher than games using preexisting assets even if the sounds are better in the premade ones.
I believe if you take Ludum Dare for example, if you use preexisting music made prior to the jam you have to opt out of the category, to make it fairer to people who spent the time during the jam but might have an inferior sounding final product.
This isn't a dig at you though, most devs wouldn't have that level of experience in music for sure. The thing that grinds my gears though (that I remember like yesterday) was in a jam I took part in where the winner in the audio category was literally boasting that they used all preexisting assets that they didn't make for their audio and thus spent comparatively zero effort, compared to people who made it during the jam. If I had been hosting that jam I would have kicked them out and scrapped their win for all the upset it caused people.