Scott was that spark for them. Scott was that spark for VR. And while the Wildabouts weren't nearly on either of their levels; even at his worst, he was that spark for that band. Robert, Dean, and Eric are incredible musicians, but without an incredible singer/songwriter/front man, they're just another outdated band living off of old glory.
I at least agree with this part of your post. Scott was that something-special that, when he had his addiction and bipolar under control, could elevate an already-great band to another level.
And I agree that STP are not gonna find another singer who will elevate them to anywhere near the level they were with Scott either in terms of musical achievement, popularity, and/or commercial success. But they might just find someone with whom they can continue doing STP with limited success. They are never going to headline festivals or sell out stadiums ever again, but they will be able to create new music and tour mid-sized venues. I hope that's what their vision is. If not, they are in for another disappointment.
On one hand, I understand that this is their band, and they obviously made a decision years ago that STP is what they want to do. And maybe it's not all about money. I know a lot of people here think that's what it is, and sure it's part of it, but maybe they also want to continue the band that gave them their careers in music. Maybe they feel their best music was written in STP, and they'd be doing a disservice to themselves to abandon that. These guys have been best friends (and brothers) for decades, and their whole lives have centered around this band, their baby: STP. It's who they are.
I've played in bands before, and even now that I'm a middle-aged family man with a day job, I still have fantasies about my old band getting back together, even after also having a band member pass away. So I get it. Only these guys are experiencing it 1,000,000-fold, and it's 1,000,000-times more complicated given their history and visibility.
As a fan, I feel like STP ended when Scott died, and anything the rest of the band does from here on out will be like an "extended tribute" to what they have accomplished.
As a musician, I understand why they are doing it, and I will support them.