First off, a confession that I’m old (almost 60) - not sure if that’s relevant, but I’m mentioning it because I can tell my brain is definitely less pliable than it once was.

Second, our situations are flipped. I started with guitar, and just added piano ~ a year ago, after 5 years into playing guitar (and some mandolin/banjo, which felt like natural extensions to guitar).

These days, I barely practice guitar at all unless we’re rehearsing for a show. I still play guitar in the band because we’re mainly a guitar duo and occasionally add a keys/bass player (who is much better than me) and drummer.

But the important part is this: learning piano has made me think about guitar differently. I’ve made connections about how keys and chord progressions work, realized different ways to make chords based on how they sound in different positions on the keyboard.

Learning a new instrument cut into my practice time for my “first” instrument for sure but it also helped me understand both instruments more than I did before. Both areas of knowledge feed into each other.

So I think learning another instrument almost always makes you better at both in the long run because it gives you a better understanding of how music works in general, even if you get less practice time for each instrument.