There's something to be said for voting against constitutional reform if it isn't perfect. The Scottish and Welsh hybrid systems are a good example. The list system hasn't prevented Labour being in power for 20 years while the North and West routinely votes Tory and Plaid Cymru, but the system ensures that while the South refuses to vote anything but Labour it will only ever mean a smattering of members. Be careful what you wish for and all that.
It's only worth voting against a reform for not being perfect if there is an extremely good chance that rejection of the reform would lead to a better reform being offered instead. That wasn't the case for the 2011 AV referendum - for which it was pretty clear that rejection of AV would be taken by both the Conservatives and most of the Labour Party as a green light to permanently continue the present stupid system.
Besides, much of history seems to suggest that democratic change is usually gradual. Systems improve incrementally. Look for example at how the franchise was extended from a minority of the population to virtually all men and women, not in one go, but over the course of many acts of Parliament over many decades. Or how gay rights have progressed since gay sex was first legalised in the 1960s - once again, it wasn't a single change that made the system perfect, but lots of incremental improvements over several decades. For that reason I personally would be very reluctant to reject something that represents an improvement on the current system (and I did vote Yes to AV, even though I would much rather a proper PR system).
Look what happened before the last general election when we had a minority government. It was chaos in parliament. Not sure I want to see that again.
I don't think you can blame that chaos entirely - or even mostly - on the Government being a minority one. The chaos happened to a large extent because the Conservative leadership at the time for whatever reason wasn't prepared to make the compromises necessary to get majority support from MPs - instead, actually alienating quite a few of its own MPs, which meant it would have ended up losing Parliamentary votes even if it had a notional majority.
2010-15 is a better example of what happens when you get no party with a majority in Parliament AND politicians who are mature enough to be able to deal with that situation appropriately. Personally I didn't like quite a bit of what that Government did, but you can't deny it was a perfectly stable Government that actually achieved quite a lot.
The real losers in recent years under FPTP have been UKIP who polled many millions of votes, many more than the SNP, but only ever had one seat.
I would argue that the LibDems and the Greens have also lost hugely - not only because they had far fewer seats than they should've done based on vote % (particularly since 2015) but also because they have lost so many votes due to people who would have liked to vote for them feeling that they couldn't because voting for anything other than Labour or Tory would represent a wasted vote under the current system.