I switched to dayjs after using momentjs for many years. Im happy about that switch, the only thing that bothers me a bit is that essential things like UTC, timezones, durations are plug-ins. If you're using script-tags with a CDN each plug-in is a HTTP fetch.
That is probably intentional to keep the core small and lightweight. You can try bundling all the plugins you use during build if you want to reduce the number of fetches.
https://day.js.org/