Express is still popular, but a lot projects these days use a full-stack framework like Next.js, SvelteKit, etc.
Fastify, NestJS (bleh), Koa, Hono are the modern replacements for express, none of them have caught on as a standard though. My personal favorite for small projects is Polka (https://github.com/lukeed/polka), when I'm not using Go instead.
IMHO the only reason you are using JS in the backend is because of some meta framework, otherwise is not worth. So at least for Nuxt is nitro, not sure for SvelteKit or the other React meta frameworks.
Next is where it's at these days in my opinion. You get a full-featured client-side React framework (the only one that supports modern React SSG), and then on top of it you get a better-organized approach to doing everything you can do with Express.
And do mean everything: I run an entire Postrgraphile server through Next (and you can easily do the sme with Supabase or a similar tool)!
Fastify, NestJS (bleh), Koa, Hono are the modern replacements for express, none of them have caught on as a standard though. My personal favorite for small projects is Polka (https://github.com/lukeed/polka), when I'm not using Go instead.