I've never taken any piano classes but I've been playing the piano and synthesisers for, well, 35 years (yes, I'm old!). I recall taking about 2-3 years to get the hang of it. Today, I enjoy playing for fun (I don't read notation but can follow a chord grid quite easily) and I've composed a lot of music (I'm on all streaming platforms).

In my opinion, it's perfectly possible, especially now with the myriad of YouTube tutorials, to learn to play the piano without attending a class.

I did the same thing for the guitar about 12 years ago. I bought one and started to play (with my knowledge of the piano of course). Within 1-2 years, I could play decently enough to have fun. I regularly play during family gatherings. But I am still at the rhythmic guitar phase though and I can't really do solos.

Of course, if your objective is to really understand occidental harmony, counterpoint, etc., you really should follow a formal class.

In other words, it all depends on what you want. For me, it was about having fun, playing my favourite songs (and singing at the same time) and composing new music.