Yeah, it just isn't happening without a massive cooperative effort over generations. Not just the time for each generation of volunteers to be monitored, but also the work needed to address age-related entropy that isn't purely "lifespan" - no point splicing yourself into tortoise-person if you spend the next three hundred years as Joe Biden.
That's a selfless undertaking for tens of thousands who will never see the benefits and might suffer some real nasty side effects. Leaving aside whether or not it should be done in the first place, it's just not compatible with the Rich Man Afraid of Hypothetical Screaming Void impulse which drives modern life extension nowadays.
I can't quite pin it down, but maybe the BG3 characters felt a bit "glossy" compared to Owlcat's? Or perhaps it's a side effect of voice acting making complex conversations drag, and lose a lot of the descriptive depth that text allows - not that they did a bad job of it!
I didn't really like any of the characters in WotR or BG3, but in WotR they felt more interesting - ah! Part of it was definitely that all the BG3 characters were like a parody of inappropriate backstories, "You would know me as Fuckslayer the Legendary Badass, Level 1", "I'm actually an Archmage, but I got knocked out in a cutscene and all my XP fell out of my pockets".