Well, keep in mind I don't write concert orchestral works much and neither did the composers I worked with when they were recording orchestras. So I'm not an expert on concerts.
But from what I DO know about concert composers:
Most of them come through academia. If you're a student, that's your best shot. Some churches might also have small orchestras.
Otherwise, volunteering or getting some other job with an orchestra and building up a network with orchestra directors and what not you may eventually get them to perform some of your shorter pieces (not much longer than 4 minutes) in a concert. If you really build up a good relationship with them, they might even start commissioning you, which a single commission could be a 5-figure amount of money. But that would probably take years of networking and essentially proving yourself.
The reason it's so difficult to get an orchestra to play new music in a concert, even if it is very good, is that orchestras have become very niche and they need repertoire on the bill that is basically guaranteed to put butts in seats; names that people recognize. If there are too many names people don't know, then they risk not selling many tickets. That's why so many concerts these days pull from games and films: It's the best source of "new" material that people will pay to see.
Honestly, you may just want to reach out to orchestras near you and straight-up ask them about playing your pieces and what sort of hoops you'd have to jump through (don't phrase it like that though).