I would say it's up to the parks to change this perception, much like Chessington did when it first opened, and it completely changed the idea of a theme park to the UK...
It's not a big question of budget really, as smaller parks are able to keep up with repaints and keeping the parks generally tidy... It's an attitude thing, and whilst Towers have started that with TLC, I still think it's because of a reaction to the crash last year rather than an actual deliberate step forwards...
They need to do things on a regular basis, reviewing everything come the end of year and actually push for a budget to fix it...