Personally I think Tera is pretty complicated. It is a whole mechanic, so looking at it in the same exact way as a Pokemon is tough and that is our normal approach for suspects, so we have to be careful here. With this in mind, over time you can draw conclusions about how it impacts the balancing of our metagame and the competitiveness/skillfulness of the format through the lens of the Pokemon throughout the format. Obviously there is the whole debate of aggressively tiering Pokemon impacted by Tera (i.e: what we have done) vs touching Tera, and I do not think it is a super linear argument as there is so much makeup behind both, but in going to a suspect, we would essentially give the community a chance to determine if the current approach is optimal or of the fundamentals need to be altered to maximize this generation's potential.

I think that Tera itself offers a lot of skillful interactions to our metagame. For starters, it rewards a lot of playing experience/knowledge as to what does what as there are so many nuisances to Tera. In addition, sequencing and the risk-reward to Tera'ing at a certain point, using a Tera offensively or defensively, etc. offers great strategic merit. There is no denying that there are more decisions made by players throughout games with Tera than without. However, it is also true that not every single decision is a balanced one and not every inference can be viewed equally as some have certain confidence and intuition behind them while others a bit less so. It's hard not to look at it a bit through the scope of how many Pokemon have been impacted by Tera to the point that they have been deemed banworthy, which you can likely say applies to Regieleki, Espathra, Volcarona, and Annihilape. It is not a perfect or really relevant (to the current metagame) to largely go off of things already banned though -- if anything, this just opens up discussion on Tera Blast, which caused 3 of those things to be broken arguably. I think all things considered: if we are looking for the most balanced metagame that results in fewer bans and aligns with the norms of prior generations, then Tera may not have as much of a place. However, if we are looking for the most skillful and completitive metagame with layers of strategy that still has potential for balancing, then Tera very much has a place. While my historic tiering insight makes me feel the former is important and we should do something on Tera, it seems like a lot of the community embraces Tera and aligns more with the latter. I take no issue with that myself.