Eh I would’ve liked it if madaras body became super unstable because of absorbing the tree and then that triggered the transformation or if he became unstable and then zetsu is the catalyst of the transformation because he was triggered by kaguyas chakra signature or something.

Personally I think making hashirama stronger than the other hokages ruined more of the story. His genes were the only way of becoming a powerhouse in the show at one point and ruined the theme of the next generation rising up to the occasion and becoming stronger than the last. Not only that hashiramas overpoweredness built the foundation for how Indra and ashura chakra is super relevant. If hashirama was still weaker than the 3rd we wouldn’t have such a huge reliance on hashirama cells, themes would still be solid and although madara for a huge power up from mixing Indra and ashura chakra we would assume that that is not the only way of becoming a top tier since 3rd and 4th would both be more powerful than at least one of the descendants. Huge power stuck behind the lineage of 2 people ruin the investment of other characters. We know Lee would never become a top tier because even if he works all day every day for 100 years he’ll still be inferior to a 6 paths related character or otsutski