One of my composition teachers once said to me, and I quote, "Good music can be made without any instruments at all." Well, I assure you that there's no point in going down that rabbit hole imo. The more you know about the idiomatic characteristics of instruments and the humans that play them the better composer you will be. Can you imagine a doctor who's only seen a dead body in text books?
100% yes, everything I've written has benefitted from my experience as an instrumentalist.
Trombone less-so than piano, but I find writing music at an instrument to be considerably quicker, more intuitive, and more organic than anything I could produce without it. Hearing physically how tones will react to each other is valuable, regardless of the eventual orchestration.
As a brass player, having an understanding of how instruments work: harmonic series, air, breathing, dynamic control, flexibility and physical limitations is helpful when it comes to orchestration.