once web-streams-polyfill release v4 then it will drop it's size again...

I don't see anything in v4 that justifies the claim that it'll be drastically smaller?

v3 have many build version to choose from
MattiasBuelens/web-streams-polyfill#82

Cool. But in the mean time there is no indication that it's being actively worked on (just incidentally), and as a user of node-fetch I do not have the option to tell node-fetch that it's installing on a normal, current version of Node and so needs almost nothing from the web-streams polyfill.

Unless npm install node-fetch can be told to install only what it needs (which as far as I know is impossible?) node-fetch is not light-weight, it's incredibly bloated, and even if web-streams-poly V4 becomes the ultimate pick-and-choose, the problem of node-fetch pulling in the full polyfill dependency will still be there. Node-fetch is a a huge library, updating the project subtitle to not make a claim to the contrary would still be a decent thing to do.

Why is this closed, the term lightweight is very misleading and it's been huge in size for more than a year now with no real indication of a solution any time soon.

It where was once "lightweight" before we decided to make blob streams spec compatible by introducing whatwg streams polyfill that will conditionally be loaded.
And it will be that once again when stream polyfill release v4 (which i hope would have happen sooner).
So i really think it's up to Mattias to fix the release as he has promised but it has taken a very long time... hence why i closed this.

On a different note, Node 18 has native Fetch API built in (it was experimentally available in 17.5) so if you have the option of using the current LTS version of Node, you no longer even need node-fetch (as well as quite a few other packages that shimmed or polyfilled network fetching functionality).