Spirit deserves to go out of business. I’ve flown a number of their direct competitors, and the experience flying Spirit was an order of magnitude worse. The management of that airline hates customers and it shows with every single customer touchpoint.
That was not my experience flying on Spirit a couple weeks ago. I don't go out of my way to fly with them, mostly because for my travel needs they're less convenient and often similarly priced or more expensive. But they deliver almost exactly what they advertise.
Fair enough, I had a very bad experience but it was the only time I’ve flown with them. I won’t fly with them again unless absolutely necessary though.