Especially since SVGs are not hinted for small sizes (AFAIK).
This is true, but the situation is no different with the main raster image formats either, and the solutions are the same either way.
I'm not even sure if SVGs are rendered equally at the pixel level on all render engines.
They certainly aren't. You're programming a graphic and then whatever rendering stack is available on the user's device will render it as an on-screen image. The quality of that render, for example when it comes to gradients or anti-aliasing, is environment-dependent.
You can use responsive CSS to switch out different shapes in an SVG to make them display better for a range of sizes. There's no tooling to automate this so it basically requires hand editing.
Then maybe we shouldn't use complex vector graphics, and instead use nice and simple uncompressed raster graphics. /s