How should they know your project is worth investing 500k? I heard they've got 3x8M, per year I presume, so 500k is a huge chunk of that. Everyone thinks their project is worth 500k, what makes yours different from the rest?
Well that's the job of VCs, that's what they're expert at.
There's also another model where established industrial communities set up research centers to fund projects that might help their common problems.
They give you 500k if you have a really good reason why you need that... and why the result is worth it... and why your project is more worth it than all the other several projects, combined, they could spend the same 500k on. Most of them are one or two people's living cost for 6 months to a year or so.
And I also do hope, if you're a human, that you're not sitting anywhere close to decision making committee be it in NLNET or any other grant program because if you do, it fits into the (terrible) narrative of software market in the EU.