Ultimately we will have to accept that playing last season's decks is going to lead to losses. It's also possible that R/G just doesn't have a card that can deal with Oketra at all (don't know, haven't looked).
That is probably right and it would be a disappointing set if you didn't need any new cards. Still, the power level of the WAR mythics seems off - I didn't make that up, this sentiment is present in the pro coverage as well (for example LR set review rare/mythic).
Now Magic has many different archetypes of decks. And while I prefer decks that win through creatures, which might be massively affected by cards like Oketra, decks like Control or Combo don't really care - neither for the powerlevel nor for the cost (plenty of mythic wildcards).
Regarding your Top8 lists, SCG Open seems to be the bigger format. It's only one event, but funny how both RDW and Esper dominate without obvious improvements (please enlighten me, does Lily alone warp the midrange matchups?) from WAR. And then we have 3 incarnations of Selesnya - as per our earlier discussions. Also funny how this can push the superior Sultai und Gruul lists from before WAR out. Though only one of them features tokens - even
Saproling Migration of all things. The others took a midrange shell and substituted black for the new bomb Oketra (best overall creature now?) and little Teferi to fight fire with fire - GG 20 minute endstep shenanigans. I had expected WW to adopt little Tef as well, but maybe WW in general isn't good enough now? Again, it's only one event - and I ignored the all-over-the-place classic event.