What would need to be done to these specific examples (and any other people want to also throw in) to balance things out? Would they need to be individually addressed or is there one or two things that can be done (and if so would it be a new/buff/nerf/change to a Pokemon/Ability/Move/Type/Mechanic)? I have a feeling I'm opening a Pandora's box but hey, what better place to do that then on unpopular opinions (as long as we keep it civilized). ;)
These are some suggestions
Tapus: Make the effect of their terrains provide only a 20% boost.
Tyranitar: Either nerf Sandstorm's Special Defense buff or just remove Sand Stream on Tyranitar altogether. I swear, without Sand Stream, Tyranitar would suffer the same fate as Kommo-o, or at least something similar.
Amoonguss: Give redirection 0 priority in general. I always felt that its kind of cheap that you can simply lead with a slow with a Pokemon and have it simply use a move in order to redirect attacks, that effect is so powerful ( Geomancy Xerneas cough cough )
Heatran: Replace Flash Fire. It already has 11 resistences, losing one wouldn't make it less useful.
Landorus-T and Incineroar: Nerf Intimidate so that its like can only happen once per battle. Landorus-T would still have an enormous attack stat going for it, while Incineroar still has Fake Out.
Charizard and Weather friends: Nerf the damage output of weather to 20%.
These are just some thoughts. Of course, these are rather drastic changes, but its not common for characters in other competitive video games to receive drastic changes to the point that there not seen nearly as in future games. In Smash, characters like Meta Knight, Bayonetta, Cloud, and Corrin received considerable nerfs to the point that their mains have dropped those characters totally.
In Pokemon, GF seems to try to introduce new Pokemon has a way to balance out characters by introducing brand new Pokemon: Looking at the new UBs, all of them have an advantage over Fairy, which is something. But that's not a really a nerf, that's like an additional option to deal with.