I think it really depends on your gear/equipment and your own eyes/ears. Every setup is different (not just in screen and speaker quality but also in internet speeds and streaming apps). Likewise every person is different in what they’re used (what their quality standard is) to and what they notice.
Streaming 4K can range from awful to very good. 4K Blu-ray will look and sound leagues better than awful streaming but might look nearly indistinguishable and only sound slightly better compared to very good streaming and not overly picky eyes/ears.
The best is to test for yourself. I’d say if you’re unsatisfied with the quality you currently have it’s worth exploring, but if you’re already really content with the quality you currently have then maybe it’s not worth the extra cost?
FYI, absolutely nothing streams in 4:4:4, and once any HDR content starts streaming with these settings it will switch away from that anyways.
These are good settings to use, but they don’t magically increase the quality of the stream.