They feel that there must be a quick fix somewhere, and the electoral system is a quick fix, but the voters themselves would resist strongly any change, particularly if it was a change to remove them somewhat from their MPs.
If you had a list system of proportional representation, a fixed list that the voters couldn't alter, that would be very different from what we have at the moment. However, there's absolutely no chance at all that a majority of voters in a referendum would agree to that, because they'd be losing power and influence over the composition of parliament, and that's what they want.