The best was actually 2010 and it boomed again in 2012 because mobile apps became popular, that was the best time to be in UX or UI design, the teams where small, people paid well and everyone was looking for a UX/UI designer. You’re worth your weight in gold during this time, I remember getting an easy 2 month contract for 40k. Now the design industry is over saturated with some talent but mainly full or posers and hacks, who bought some books, or listen to some pod casts and they call themselves designers without having actually built anything. I have always been an “everthing” designer to stay relevant(ux, ui, visual, motion..etc) it takes years of bouncing around in different design areas, then spending time practicing the craft in each vertical. I suggest every designer try other positions in the design world, step out of your comfort zone and build new skills, you will be relevant/competitive longer in a fast paced, and evolving tech landscape.