Courses are a shortcut to getting where you wanna be. They don’t stop you from having to practice til your fingers bleed, but they will give you enough of a head start to be practicing the right things, rather than first finding out what the right things are, which (being an old vinyl hand myself I know from close experience) makes for many lost hours of practice.
A relatively cheap course like the How To Digital DJ Fast can be finished in 6 weeks (at a realistic pace) and will give you a great foundation to start practicing and building experience on.
Invaluable from a time or money point of view.
Good luck.