No, it’s not that simple, you can open the SVG and convert it to stitching but that rarely produces a good working file without some extra work. There isn’t a software that exists that can autodigitize reliably, some simple designs will work ok off the bat but most of the time you’ll need to make adjustments to the stitch directions, pull compensation, underlay, density, etc.

As to why people buy more expensive softwares: simply that they’re better programs. Inkstitch is fine for what it is, but you get what you pay for. I haven’t used inkstitch but I do use Inkscape on a rare occasion and find it incredibly clunky and difficult to use compared to Illustrator. So I imagine it’s much the same for Inkscape, plus there’s likely features that exist in the pricier softwares that aren’t available there. That being said, great way to dip your toes into digitizing before you make a bigger investment, and maybe for what you plan to use it for it’ll suit your needs just fine. But don’t be surprised if you outgrow it quickly too.

I highly recommend spending some time embroidering designs from reputable digitizers/designers before you start sewing your own. You won’t fully understand the process until you’ve seen it in action, a design can look great on a screen and sew out as garbage. Try some files from Urban Threads, Embroidery Library, or John Deer to start (lots of other good options out there too, just avoid places like Etsy in the beginning until you learn how to spot the lazy digitizers.) By starting with quality files you’ll be able to get the hang of everything else with your machine easier and you’ll learn how a good stitchout should look.