There seemed to be an expectation after the last GE that changes were going to be noticed virtually overnight. Rather than trying to instill some measure of realistic expectations the government has since gone down the path of constant u-turns to try to get positive press.
I think maybe it's the unplanned knee-jerk reactions, inconsistencies and U-turns that are making people question the current Government rather than the speed of improvement.
If the public believed that improvement was really going to happen I don't think we'd see the dislike of the current regime.
But eg Winter Fuel Allowance err wasn't mentioned in any pre-election campaigning. Lifting 2-child benefit cap raised and MPs thrown out of party only for it to become Government policy not too long afterwards. Perpetual U-turns gives the impression they really don't know what to do, sort of "Something needs to be done, this is something so we'll do it ... <few days> ... oh dear, lets undo it and do something else ...".
No confidence things are ever going to improve more so that not yet seeing improvement.