Scientists don’t know if dark matter really exists, or if there’s other ways to explain this phenomenon. Another explanation is that there’s no extra matter, but that this is just how gravity behaves in large scales.

I am by no mean an expert, but I When I was a master student, I spent some time exploring the modified gravity rabbithole the most popular being MOND. The big limit is that it’s a ad hoc model to fit galaxy rotation curve, it works pretty well. But it doesn’t work if you try to use it for a cosmological model, and doesn’t explain gravitational lensing. Making it an overall weak hypothesis compared to the good old cold dark matter

The standard cosmological model with dark matter and dark energy (it’s two different objets) is supported by a lot of evidences. Up to now, no alternative theory works at explaining all data we have.

Don’t get me wrong, we may have a massive hole in gravity, and may at a point get the missing piece of data to find it and explain everything without using exotic particles. But as of today, both particle physicists and cosmologists agree that particle physics beyond the standard model provides the most solid candidate for dark matter and that nothing else has a solid backing