Part of the problem is the all-or-nothing approach when it comes to disability benefits.
I get ESA, HB, and got PIP on appeal. Since getting PIP, my weekly income after rent is 2.5 times what it was before.
On ESA and HB I have a large rent shortfall as am expected to houseshare but having my own flat is a huge stabilising factor in my mental health. Being eligible for PIP means my full (still low!) rent is paid. It also means the PIP money itself, as well as a premium on ESA.
So without PIP I really struggle, but with PIP I have plenty*. It's so all-or-nothing. Because they've cut elsewhere - eg. HB for under 35s, mental health services (so have to pay for therapy), it makes the difference so much greater. It really is like there's a little group of people who get the funding and the government can point and say "look, we're supporting the disabled", whilst anyone marginally less disabled - or more likely, more unlucky/less educated/able to fight decisions - can go to hell as far as they care.
*I'm used to being skint so have simple tastes, don't have a car etc. Which is good, so I can save a bit for when they decide I'm not eligible and I'm back down to the breadline... And in the meantime I can actually pay for things to improve my mental health and employability, like therapy and education, as both are otherwise unaccessible since public spending cuts (adult education no longer offer reduced fees for Support Group ESA as considered "too far from workplace" to bother with us).