I always forget my own arguments, but here’s a tl;dr for something that hasn’t been written yet. Admittedly, I am not a Limited player so my focus is not there.
-Green gets parasitics in a one set block world, when even in multi-set worlds parasitics are still an issue. (Energy, Explore package recent examples)
-Multicolor is a strictly better Green. They get Green’s creature sizing and additional benefits for the “cost” of having to play at least one additional non-Green color.
-Multicolor’s higher power level means stronger answers are required to answer threats. This actively hurts Green the most of any other color since Green as printed gets the worst answers.
-Necessary color fixing for multicolor formats remove one of Green’s old uses. (A fully fleshed-out blog post absolutely would mention Tom LaPille cutting Signets from his cube years ago and how a ton of people thought he was mad for doing so.)
-Above point leads to significantly more dangerous point: other colors gain way more from splashing Green than Green does from splashing other colors. Since Multicolor is “the most popular mechanic” (I think MaRo said this but my ability to google things is not strong enough to find it.), WotC is fundamentally committed to shitting on Green every X years. See: current ramp strategies. Why does Green not get enough of its own payoffs for ramping? Is Hydroid Krasis really Green?
-(Aside on previous point: despite the mathematics telling us otherwise, I believe a Black deck splashing, say, Assassin’s Trophy, gains a lot more than a Green deck would gain from a Trophy splash, at least how the color pie stands now.)
-Even more from previous point, Green cards get costed as splashable too often. I was actually going to praise WotC for putting Cavalier of Thorns and Vivian, Arkbow Ranger at GGG costs.
-Green naturally loses to its own enemy colors (U/B, specifically counterspells or removal on curve) unless given massive hosers (Veil of Summer) or the ability to get ahead of the curve (one drop accelerators).
-Green is very soft to planeswalkers, especially since the bulk of Green’s card drawing is given to Green only because WotC prints something busted.
-The game has evolved to be built around playing to and answering the board. Is the refusal to give Green the tools to do so why Green is given busted card drawing instead?
-Wicked Wolf might be too toxic but why can’t Green get a weaker FTK at 1GGG?
-If Green is supposed to be able to fight against unnatural interference like Planeswalkers, spells, etc., why doesn’t Green have something like a weaker, unsplashable Negate at GG? Actually, why are we still creating conditions (*cough* three mana Planeswalkers *cough*) that require the constant reprinting of Negate or Duress? Don’t we need to remove some of other colors’ power here? Are we supposed to expand Green’s pie, shrink everyone else’s pie (except for probably White), or both?