Amen!I cannot emphasize strongly enough the importance of playing other TTRPGs than whatever one you have been playing non-stop for years or decades.
I know, that game is like an old sweater. it is so comfy and it smells like your youth. And I am not saying throw it away.
But you absolutely WILL learn things about yourself, your group and your favorite game by trying something new. And I don't mean "try" as in a one shot. i mean play a campaign in a different game. Spend weeks or months delving into a new game and its nuances and quirks.
There is nothing wrong with liking what you like, but there is real value in trying new things and letting them inform you about your own preferences. This goes for food and film and towels and vacation spots and absolutely goes for TTRPGs as well.
How do you pick a new game, though? How do you decide what to play and how do you learn that game?
Luckily, we live ina time of abundance when it comes to both games and ways to learn them. Pick a game based on your other preferences: genres and media you like is an easy one. Or, read one of the ten thousand blog posts about "games that aren't X' and pick one that sounds cool and fun to you and your group*. Then, go to YouTube or other another content platform and look up videos of how to get started, actual play videos, reviews and so on. There is so much content out there, even for relatively obscure TTRPGs.
*But my group won't change games, you say. Okay. I get that. Play solo, then. there are a number of great solo TTRPGs, as well as a huge number of tools for playing any game solo.
Experiencing other TTRPGs is guaranteed to improve your TTRPG experience. Maybe you will find a new favorite game, but even if you don't you will come away with insights you could not possibly have acquired otherwise.
When I started in the hobby in 1977, there weren’t a lot of choices. AD&D was first, and that was my ONLY for at least a year. Then I moved and got introduced to Traveller and The Fantasy Trip/In the Labyrinth.
Another period of experimentation stagnation followed until Champions was released. And I got Stormbringer soon after. And I didn’t buy or try another RPG until 1990. I started law school in Austin, TX and got into buying some games from a shop’s discount bin- SSI’s Universe was first; others followed.
Shortly after that, I found a game group in my new city. Because of a particular set of circumstances*, we tried dozens and dozens of systems over the next few years, including some playtests. By the time I moved away in 1994, my RPG collection had ballooned to more than 100 games.
And I can absolutely discern a difference in the way I designed & played characters or approached running a game.
* I can explain if asked.