I am a YABU. Not because I am evil and think it is OK to treat people like this but because your OP is not thought through. So you "hate UC and PIP" Bravo! Virtue signalling.
We all hate it. No-one wants to be on it, or be assessed for it. No-one is going to say "Oh yes I love my PIP assessments".
Let's say we abandon them and let everybody have it who wants it without an assessment. Let's say everyone can have UC without an application, a work coach or a means test. Great. Now everyone pay extra tax to pay for that. Happy with that? (It would have to be an indirect tax as income tax wouldn't cover it). (Or shall we just let "the rich" -ie not us) pay for it.
Think it through OP. How would you run the system? How would you decide who got what and who paid what? How would you decide the level? £10k a year? 20k a year? More? Including or not including Housing Benefit for rent? And if I really don't want to do more night shifts at Amazon can I just claim UC instead - beacuse I am telling you night shifts at Amazon are not how I want to spend my time.
So that's why YABU. Neither is a great sytem but nor is it anywhere else in the world. How should we change it?
(Me I would go for a Universal Basic Income - but that is unlikely to happen anytime soon).