Export for Screens seems to be missing a few things to be able to replace Save for Web (Legacy), which is a strong limitation since Export for screens have features Save for web doesn't: Support for exporting multiple scales / resolutions , which is a must in 2022 with responsive images on the web.

One area it is lacking in is support for slices (by priority):
1. Be able to export only a selected slice
2. Be able to split up export for screens based on slices