I get what you are saying - and almost fully agree with it. I do agree the 'last second switch' of Butcher in the "climax" of the season definitely felt unearned and a "wha?" moment in the writing. I also agree that the assumption everyone was making, that the child of Homelander, wouldn't be able to survive *most* of what was going on in that building, was also 'bad writing'. The only caveat I'd say here is that - at least in regards to the power SB was releasing - a power they *believed* would stop Homelander, its not a big leap to then think/believe it would harm Ryan, IF the expectation was it would harm Homelander. (But only /that one power/ I could buy would be seen as the threat, not everyone else's).
The only real thing I "disagree" withn(and even that is a harsh word lol) is your description of Butcher "being unable to fully love and support" Ryan as to 'why' he pushes him away after the start of the season. Because I saw that scene as Butcher doing what was "best" for the kid, and NOT for Butcher or because of his own issues. I saw him pushing Ryan away as an act of protection (from Butcher), because, and I believe Butcher says this directly at one point, he was afraid every time he (Butcher) visited Ryan he just exposed his location for Homelander to discover. At that juncture Butcher believed Ryan's location was protected/unknown from Homelander and no longer felt it worth the risk to Ryan to keep visiting that way.
Now, of course, the way they write Butcher - Butcher couldn't be honest and just tell the kid that - but had to do it in an asshole way. (because direct communication would be the ending of most tv shows - lol) But that Butcher didn't bail on the kid because of his own personal demons, or resentments to Ryan about his mom, etc. But only and entirely because Butcher wanted to keep Ryan's location secret. So in Butcher's mind (for the end of the season reactions) he never stopped protecting Ryan, he just felt he could only do it from a distance.
But I also agree it was all a mess of a "not earned and still not paying out" finale. There were upteen ways they could have made the attempt to protect Ryan and NOT turn on SB to do it, or not end up with Butcher defending Homelander to do it. But the writers didn't go any of those ways. THIS was the crux, the crisis, they clearly wanted to ramp up to for next season. They just didn't go about it very well.
And I'm not sold Ryan is "full evil" with that smirk of a smile at the end of the finale' episode. I do agree they are setting Ryan up to be a "Which way does he ultimately fall - good or bad" question character - but I'm not sold that they've already fully committed him to the dark/Narcissist. I expect him to show favoritism for the Homelander Way - as long as the public Ryan's exposed to continues to show that support/applause/adoration for Homelander's actions that he saw right then, in that moment. And to be honest, that is a natural and logical position of any child to that sort of reward/consequence - if their (the child's) selfishness is applauded, they will continue to engage in the behavior, and see nothing 'wrong' with it. Morality lessons don't happen in a vacuum. However, I also fully expect at some point Ryan will be asked (By Homelander or maybe by Vaught) to do something he just WONT do - and at that point - their 'break' will happen and Ryan will get redemption and then go work for 'the good guys' instead and/or then try to navigate a line between "good" and "saving his father". I don't at all believe the writers (of the tv show) will leave Ryan to go evil, stay evil. There's no meat on that storyline.
I still enjoyed this season though, despite the 'pointless' storyline for some of the minor characters that went nowhere and the not-so-great climax 'ending' of the season. The journey to get to that point though was still fun and we were still entertained by all the episodes. Just hope there's better development (or an actual ending) for some of those hanging-plot-pointless-characters next season and that we get a well-written lead up and 'climax scenes' at the ending, whether its a series or just a season ender, next year.