To me, the definition of on fire would be that if you list a home that shows well, and is priced at a list price that is commensurate with recent sold comps, that the home will sell quickly. Additionally to me this definition also means that it is very hard to find a home and get a discount on it. Discount meaning you get it under market comps and that the home is not thrashed. That you got that discount because of the overall lack of activity in the market.
Note this does not mean you can put any home on the market at a premium that doesn’t exist (which is happening ALOT now).
So if you contrast my definition to a few years ago when plenty of people were putting homes on the market that showed well and were priced correctly and sat due to the psyche of the buyers or how there were many more reports of people getting homes at discounts due to large inventories and a collective psyche of fear, then I think it could be argued that many submarkets have gone from poor to transitional, to hot markets.
Again, distinguishing that getting a home below list price does not necessarily qualify it as a good deal, especially if the home was not priced right.