Almost everything you need to create vector art, SVG doesn't support.
Multiple outlines in a single shape? No. Varying thickness in an outline? No. Rounded corners on arbitrary vertices? No. Non-destructive boolean operations? No. I'm not even sure SVG supports paragraphs.
Many of these Inkscape implements as live filters, which are saved as SVG extensions in the XML .svg file that nobody but Inkscape can properly load.
SVG is ridiculously bad as a creation format. It's a good format to export to, but as a backend and it's just insane. It's like using a single PNG file as a backend for your multi-layer 128bpp raster project.
I use Inkscape a lot but I can't help but notice that the best vector art illustration come from Affinity Designer, Corel Draw, and Adobe Illustrator. If you compare the quality of artwork made with proprietary tools to those made with Inkscape, it's very clear that Inkscape severely limits what artists can achieve. You can easily create complex illustrations in other tools that would be a nightmare to manage in Inkscape. Just compare how you clip something in Inkscape to how you do it in Affinity. It's ridiculous how different the two workflows are.
So say you want to make something like a wall with a tunnel/cave and a road in it. You can draw a rectnagle, a circle, put the circle inside the rectangle and it's clipped, then use a triangle for the road and put it inside the circle and it's clipped.
In Inkscape you need to select both shapes and use clip group. Which shape clips which depends on which shape is above the other. I can't tell you which one sould be above, by the way, because I never remember it. If you want to clip one shape by another shape that is already inside a clipping group, you have another problem because you need to double click the group to be able to selected the clipped shape. The more layers of clipping you have, the more you have to double click.
The layer structure is also different. In Affinity, the shape itself is the group and occupies only 1 line in the layers window. In Inkscape, every clipping group creates 3 entries in the objects window. One for the group itself, one for the shape at the background, and one for the shapes being clipped. So in Inkscape you have something like:
g277 (this is the group)
-> circle
-> Clip
---> rectangle
In affinity you have:
rectangle
-> circle