As a newer Smash player and Falco main, I am a biased to say Falco is still viable. There are definite pros and cons to him, however the idea that he's "dead" or "unviable" is totally wrong. PPMD recently posted a video to YouTube talking about Falco's place in the Melee meta (
https://www.youtube.com/watch?v=k8y0U3EWrqY), and it makes perfect sense. It's interesting to see Falco's lack of use since there are definitive reasons and techniques that allow him to go toe-to-toe with Fox, and Falco players can still compete and win at a high level.