Kinda yes, kinda no. There have certainly been times, particularly after 9/11 and various crises, when demand dropped significantly.
There’s also airliners that just haven’t sold well. A340NG, A380, 747-8, 767-400, the MD-11, until recently the Cseries/A220. The A330neo has also not sold particularly well and you could probably get a slot within a year easily.