They are and they aren't. Everton knew what the rules were and carried on spending even when they knew they were going to be in trouble by doing so. As you say, entirely their own fault and no one should have any sympathy with them.
The problem is that applying a 10-point deduction mid-season is an issue, both in terms of the timing and severity. The commission made the rather ridiculous point that a financial penalty was inappropriate because they had a rich owner. That shouldn't count in applying an appropriate sanction.
They also said that a points deduction was appropriate because their excessive spending could have resulted in them accumulating extra points they might not otherwise have got if they'd restricted their spending within acceptable limits. You can see some logic behind that but then united have spent loads and under-performed whereas Brighton haven't spent loads and have over-performed. So spending more does not necessarily equate to accumulating more points.
The main problem with any system based on historical profit or loss is that it doesn't really give you a meaningful insight into a club's financial position. United needed investment because they were burning through cash. Without Ratcliffe's money, they might well have run out of cash by Easter. Hard questions should be asked about their liabilities, and how they're going to meet them. And the same applies to every other club.
The historic basis of PSR is also questionable. If club A reports a loss of £75m in year T-2, a £40m loss in year T-1, and a £20m profit in year T, while club B reported the other way round (£20m profit in year T-2, £40m loss in T-1 and a £75m loss in year T) they'll both pass PSR in theory. But which one would ring alarm bells?