A dictatorship can be considered sustainable in the short-term, somewhat paradoxically. However, oppression of a population will always lead to revolution, provided the population isn’t incredibly happy.
I live in the UK, and see the huge policy shortfalls as a result of Parliamentary limits. Government can only ever provide 5 year funding promises and 5 year plans, creating uncertainty for schools and hospitals. The UK is very close, but these issues are larger than they may seem.
In addition, the tumultuous events of the past few days in British politics and the huge fiscal dilemma the country finds itself in are exposing huge flaws.