I work with internal systems for a living. As an end user, you’re not the primary customer - finance is. Concur is by no stretch amazing, but it works fairly well on the back end where your expenses come in, route for approval, get paid, get accounted for, etc.
I’m not trying to be dismissive. I absolutely try for the best internal user experience across the board, and it’s led me to try a lot of the shinier startup T&E systems. But Concur works well for finance and accounting, and frankly, it’s also cheap - something you also have to factor in G&A tooling. Those two factors together have overcome my desire to rip it out at a couple of different employers.
And given the price sensitivity for a tool that does not generate revenue for its customers, it remains a tough space for new entrants to disrupt. It’s not enough to make it good, you also gotta make it cheap. When I’m done with the startup carousel, I might try my hand at this - but you should bet against me!