This thread has been running with mild, mayo-level spicy takes lately, so I'm bringing out something to stir the pot a bit.
The Toxic TM nerf wasn't bad by itself, but it was kind of excessive. Many defensive mons suddenly lost a major way to force the game to progress, so I have a compromise. Toxic back as a universal TM, inflicting regular poison, unless used by a Poison-type. (Alternatively, Toxic back to universal TM status, and the regular Poison-type poisoning status moves inflict bad poison instead.)
yeah unfort this would be worse. It's basically a targeted attack against the non-Poison Type mons who still learn Toxic. I'm a huge fan of the Toxic change, and I think they did an excellent job (for the most part) working out which Pokémon retained the move. A nice side-effect is that, besides Gliscor (and Mew/Terapagos), all the non-Poison Pokémon to keep the move are also pretty weak which gives them a bit of a USP.
Besides Breloom, Zoroark, and Houndoom they also only put it on Pokémon who could have a real use for the move. Bellibolt, Hypno, Dudunsparce, Gliscor, Goodra, Mandibuzz, Quagsire, Spiritomb, Toedscruel, Trevenant, Umbreon, and Vespiquen all have a slow and bulky stat spread. Not all of them actually opt to use it, I don't think Dudunsparce, Bellibolt, or Goodra often do, but it feels like some actual thought went into its distribution and they wanted Toxic to form a part of the playstyle identity of these mons. Looking through the list of who I think could pass the flavour bar in Gen 9 I'd say it's only Rabsca (thanks to Rellor), Pincurchin, Magmortar, Polteageist, and Brute Bonnet, and all of these mons are supposed to be doing different things to Toxic stalling. Well Pincurchin probably could try and Toxic stall, they took Rising Voltage from it and now it has nothing better to do, but that's an aside.
The mons that don't fit this and still get the move are actually quite interesting though. Breloom makes sense, it has Poison Heal it kinda makes it mandatory. Zoroark isn't particularly poisonous, it has always learned Sludge Bomb, but I think that might actually just be them being cute and wanting players to Illusion as mons who used to learn Toxic but don't anymore to surprise players.
I'm curious looking now at Houndoom keeping Toxic but Magmortar losing it. While Magmortar has retained Smog, Clear Smog, Acid Spray, Poison Jab in Gen 9, Houndoom only ever had Smog, Sludge Bomb, and Toxic itself. It has less of a claim to the move than Magcargo, who still learns Smog, Clear Smog, and Acid Armour. Considering Zoroark, Umbreon, Mandibuzz, and Spiritomb all keep the move as well, making Dark-Type by far the most represented type besides Poison-Type itself, it seems they might be trying to share the move with Dark-Type a little bit. Umbreon and Mandibuzz are slam dunk catfits anyway, but Spiritomb, Zoroark and Houndoom are varying levels of borderline so the fact they share the Dark-Type feels relevant in some way. But if they were really trying to do that Scrafty would make sense as an inclusion, its spit is stated to be acidic in its debut generation, it learns Acid Spray, Sludge Bomb, and Poison Jab, and it even has great bulk and Shed Skin to possibly Toxic stall, so eh maybe not.
Overall though I like the change a lot, not from a gameplay POV but from a flavour POV. It feels like a cool category to still learn Toxic for the mons that do.