The main problem is safe seats.
Regardless of the political party, safe seats are ignored.
I live in a Labour safe seat, been Labour for over a century, they could put Ian Huntley up as a labour candidate and he'd get voted in, the result is nothing gets done because labour are going to win if they spend 200 million on the town and they'll get voted in if they spend fifty quid.
Those 'red wall' towns that are now conservative will have masses of money spent in order to try to secure future wins, likewise all marginal seats, swinging from labour to conservative, each one will try to sweeten the voters for next time.
Safe seats get nothing, they stagnate and are left to decay because they don't matter, the electorate will never waver and so nothing will ever change