I just read through their announcement and it seems reasonable, material icons are overused and OSS icons available don't provide design guidelines for extending (which they do).

I'm not a designer and haven't looked into alternative but this sounds like a good effort and I like the look.

I was recently involved in a project which used streamline icon pack, and while that set is huge and I don't mind paying for value - their licensing scheme is ridiculous - 3 licence tiers where the limitations are arbitrary and ridiculous and actually useful licence option is "contact us for a quote". Also they expose a private npm repo that requires per user token (per licence) with account for each developer (even those that just run frontend). We ended up removinh their icon set after paying upper 500$ tier - it's just not worth the hassle.

So if this is open source maybe some designer would accept commission work - eg few hundred $ per icon/or w/e per set and then that gets added to open pack I like the idea. Or if some designer working with them upstreams their additions.