>>“nifty 50”... default lens you learned to shoot with... because a 50 mm lens most closely matched what your eyes see.
Sorry to be 'that guy' but our eyes see more like 35mm. 50mm was popular because it closely matched the image circle needed for 35mm film (the diagonal of a 35x35 square is 49.5ish). You may have noticed that the size (and cost) of 'FF' lenses go up as you move away from 50mm.
That said, as a landscape photographer I learned a lot from my mom's landscape paining magazines back in the 60s. If you're doing landscapes as well I'd suggest searching Youtube for 'Adam Marelli' as he's had a couple of B&H couses that were quite good - and he's had quite a bit on Udemy (not free). All very good. I haven't seen anything recent from him there, no idea if he's still as interactive with students taking the courses as he was a few years ago.
On, and for me, it's gotta be Monet. His studies on the qualities of light resonate for me. Ditto Rembrandt, particularly his portraits that have a single source of light.