Generation after generation the Spartiate class was shrinking, and the Spartan rulers did nothing to stop it. "Why?" is the question we should be asking, it's obvious that when you're part of an elite class dominating society, and the number of fighting age men your class can field is declining from thousands to hundreds, that that's going to be a problem some day... Yet they did nothing to stop it until the whole system crashed.
That's the lesson we should be learning from Sparta.
Mostly, though, fascism is ineffective.
There has been one successful slave revolt in recorded history and it wasn’t in Sparta. Legislators can be selected any way that leads to state survival in the end. Estate taxes have bugger all to do with austerity.
The Spartans aren’t pawns in our current political drama. They existed for themselves not for us. A great deal in how they lived was odious but they were no more fascist than they were Christian.
I don't really like your "one successful slave revolt" statement, because it depends on the meaning of "successful" and "slave", so it seems interesting at first, but it is not really possible to think or argue about it without restating it in a clarified form first (even though there is some truth in the statement). I suppose you were thinking about the Haitian Revolution?
[0] https://acoup.blog/2019/08/16/collections-this-isnt-sparta-p...