Save For Web was marked as "legacy" when Export For Screens was added, with the implication SFW would be vanishing at some point. It's seven years later and SFW is still around, and still what I use 100% of the time over EFS and the terrible Export As... options.

Save For Web is a great tool for someone creating art with Illustrator; it lets me quickly and easily adjust the file format and resolution of the generated image for whatever I may need, and uses most of the screen to show me exactly what I'll be getting.

Export for Screens? It's terrible for my needs. One tiny little thumbnail for each artboard. Or each "asset". Which I guess are useful if you're making user interfaces? I don't do that, I use Illustrator for illustration.

Export As...? It's even worse. Each file format has a terrible little dialogue box without much consistency between them, and next to no control over the final size - guessing at final pixel size by changing the DPI is utterly absurd to do. It used to be useful, years ago; it used to be as powerful as the dialogue Photoshop gives you when you try to import an AI file. Then the whole UI got rebuilt and that was thrown out in favor of a bunch of dialogues that do the barest minimum effort required. Now it's just a bunch of bad jokes.

Save For Web is the only one of these options that's really useful to an artist, and you hide it away by saying it's "legacy". Obviously not something anyone should USE.

Please, do what you have to do to make Save For Web something you don't want to mark as "legacy". Keep it around. Modernize it so you can drop in new file formats as the world decides they're useful. I really do not know what I'd do if you ever did finally follow through on the implicit threat of removing it; exporting stuff would be a huge pain **********.