I use it for a lot of stuff. I roast pork on top of mirepoix, I make soups with it, pasta dishes, I make it alone with lots of butter and herbs and then blend it and use it as a rich sauce, I don't blend it and then serve it as a side with chicken and fish (adding rice is an option here), add bell peppers and make gumbo, use it as a base for braising basically anything... I do truly just start a mirepoix when I don't know what to make, then, once it's started, I dig around for other ingredients. It's so forgiving and really just makes almost anything more savory and flavorful.

The last time I made it (Saturday), I ended up transferring it to a roasting pan, then roasted pork. I took off the pork when it was done, then while it rested, I deglaced the pan with white wine, put a portion into a pot, added ketchup, vinegar, etc. and used an immersion blender to make a bbq-style mirepoix sauce. Shredded the pork and made pulled pork. It was a huge hit with the family. I know mirepoix-bbq sauce sounds a little weird, but it was incredibly good.

It's an very versatile base, which, I think, is why different food cultures all have a version of it. And you can do a lot of different things with the same base just by changing the technique. Smaller or larger chop, longer or shorter sautee, add ingredients to change the character (classically, tomato paste to make a pinçage, but you can also swap it to a Holy Trinity or sofrito very easily), and so on. It's a great thing to play around with.