WordPress can either be forced to accept SVG as a MIME type (undesirable approach - security issues) or a proper plugin can be used which both allows use of SVGs and sanitizes them - preventing code injection attacks and so on: one with a good reputation last time I was looking into this was Daryll Doyle’s SVG-Sanitizer.
Short of doing either of these, the SVG is being rasterized on the fly by WordPress upon initial upload, and so is easily pixelated based on in-browser scaling / zooming and other factors.
Also bear in mind that a pure vector SVG doesn't really have pixel dimensions - you can control the wrapper/container/div in which it's encased, and that can be sized per pixel or percentage, but a pure vector SVG graphic element is completely resolution independent and freely scalable - hence the S part of SVG.