Could be much more refined.
I realise that you could not get other voice actors and I feel for you. But the predicament that this left you in hit the animation pretty hard. A lot of the voice acting just didn't hit the spot for most of the characters.
Altogether the plot took a long while to go very little distance. There was too much random things happening as well that distracted from anything meaningful and added nothing. The hot air balloon for one. Or the black teacher. For the distance the plot goes the 20+ min length was far too much to ask for people to sit through. I could see how the characters were parodies of japanese anime but the long school bit was very american in style and made the characters out of place.
There was no overall series structure given either. The main character had no big dream or even a goal. There was no love interests and the rivalry is very forced. There is also no greater threat established OR any relationship growth between deulist and morphemon. While these are not needed for a comedy flash they are all big parts of what I imagine you were parodying. So much material could have been drawn from these sources.
Some parts were good but the presentation and acting usually muted the impact of any comedy. I could see what you were getting at but there was a lot holding you back. And to say this was years in the making I would have expected something polished and refined. This just seems to fall flat in a lot of areas. Maybe even quickening the pace on this flash would have helped. It could have started off in school. The don't get their til about a third in.
Anyway I think this could have been greatly improved with better voice actors and better pacing. You didn't need to explain everyones background in one episode. Characters usually get their own episode for background exploration. And I understand if you could not get other voice actors but it is still a fact that the lack of them was a big flaw in the animation. For me it was the biggest.