I find it sad that so many people see politics as soap powder. Tried Brand A - not happy with it. Tried Brand B - not happy with it. So I'll try Brand C.
On that basis, you might as well vote for the Communists, as they've not been tried out in the UK. Daft? No dafter than voting for a bunch of shysters and tin-pot fascists.
Here's a thought. Maybe Britain has intractable problems that no party can solve in a short time. Maybe as a nation, we're in a spiral of decline that's almost impossible to halt. (Think Austrian Hungary, pre WW1, for a working example.)
Or to put it another way, if a qualified plumber is struggling to sort out my plumbing, is it sensible to replace him with a vacuum cleaner salesman out of frustration?