My old portfolio written is NextJS is getting on a bit.
I've always been happy with NextJS for production app and in particular very happy with their statically generated bundles.
However the big issue with NextJS for me is React itself. For regular use it's been great, however since v16 React and their api has become clunky, insonsistent, and patchy.
Look at useEffect documentation for clear example of poor judgment.
Svelte and more so SvelteKit build onto of everything good that was introduced by React without any of the suspect API decissions.
Plus with SvelteKit I get a portfolio project that is closer to web api and vanilla Javascript. Much closer to my current views on web development.
Alan Ionita