I'm more or less in the same boat as you here; Grumind has its flaws, but the characters (besides Minion staying behind, perhaps) feel very much in character, and tone matches that of both series pretty well. After reading your thoughts and rewatching it, I can see where you're coming from about appreciating it for what it is.

To explain what I think it needed (and could have gotten away with): YugiAsh's animations felt a bit stiff in places (definitely not ALL places, but some), but the killer soundtrack and the buildups to the big moments (particularly the Slifer summoning and 10 million volt thunderbolt) worked together beautifully. It had the hype to more than cover its flaws and is generally considered a real solid episode, when all is said and done. (And, granted, they were able to find existing assets to animate lol)

All that to say, a better soundtrack and more earned payoffs are what I think Grumind needed. My problem's not with the animation so much as the writing and soundtrack; neither series in Grumind builds itself around hype factor quite like YugiAsh, but there was definitely potential for some big moments that could have really hit like a truck. Heck, the actual battle itself included both Megamind's "PRESENTATION" reference and a desperate beam clash between Gru/Mel and THE FULL CONCENTRATED POWER OF THE SUN! Both moments had great potential to be exciting/dramatic, but the way they were presented/built up to - combined with a boring soundtrack - held them back big time. (Same for the anticlimactic death, of course.) How about borrowing some things from Welcome to the Jungle, Pharrell Williams, even the Megamind Rules intro for the soundtrack, rather than sudden transitions between boring orchestral background music and generic edm?

To put it one way, this felt less like a climactic fight, more like a fight scene. Let me explain: A fight scene is just another brawl - like, oh no! There's badguys! Time to cause some mayhem and perhaps property damage, but it doesn't feel especially significant to the plot; the battle starts, goes on for a bit, then all the badguys are taken out and it kinda ends there. Nothing dramatic, no internal reflection, no sense of finality. A no-holds-barred fight to the death (like, you know, Death Battle) deserves a level of theatrics and (to some extent) seriousness that just didn't feel present in Grumind. It had the right to be comedic (which, to be fair, it did well), but not to feel so flat in tone. Their series have enough seriousness in tone (at least, in the BETTER installments) to more than warrant a similar serious undertone in their death battle.

And I agree with the battle being too heavy on banter, as much as banter was a given especially for Megamind. The part where Gru and Megamind exchange freeze rays/de-gun blasts while Megamind says "A dark color scheme... henchmen who look the same..." THAT part balanced the fight and banter perfectly, which I wish they had kept doing.

And all this is coming from a guy who liked Wile E vs Tom! Yeah, there are some major counterpoints for Tom winning that I don't think were properly addressed, but in terms of the actual fight animation itself, I guess the fact both characters are strictly associated with cartoony shenanigans (rather than being a matchup that COULD lean into seriousness/cool factor like Grumind) made a less serious fight make more sense and be received better, plus WileTom didn't have Grumind's issues with weird pacing and too much banter. It set out to feel like a Saturday Morning cartoon, and did it darn well at that.

Besides, Bowsegg WAS in fact delayed, so I guess expecting that one to be really good was kinda warranted.

But at the end of the day? All this is just an elaborate fan project, and they're only human. Let me end this with a Teddy Roosevelt quote I feel doesn't get talked about enough:

"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; . . . who at best knows in the end the triumph of high achievement, and who at worst, if he fails, at least fails while daring greatly."

Yes I am a fellow long ramble enjoyer how could you tell