They need to be, but many plugin developers simply break the GPL.

Sure but developers would still add licensing checks, hosting some dependency offsite, or other obfuscation to try and force people into paying for the plugin

It just doesn’t work. Anyone who wants to will take it. I don’t see this problem going away

I have served many clients with wordpress sites who would much rather pay to license a supported plugin than use a "free" plugin they have to support themselves.

And then the authors realize this and make the free plugin a nightmare to manage to coax folk into paying for it

That is the entire business model of grafana

If they just use the api to create the plugins, no. (It's like Google vs oracle and the java API)

It's the position of wordpress that all themes and plugins are derivative work https://wordpress.org/about/license/

My understanding is because of the way PHP works all plugins are directly interacting with the wordpress code.

I understand, but if I create some code that use no wordpress code and only API access and don't ship it with wordpress, they can't enforce a gpl licence for my code.

Wordpress does absolutely nothing to enforce this, so their position on the matter is irrelevant.

Commercial plugins are a thing, next.

No.

Yes.

There exist many WordPress plugins that are not GPL-licensed, or plugins that are ostensibly GPL but are merely wrapping things (either code or APIs) that are not GPL, which isn't exactly a compliant use.

Whether we like that is not the question I was answering.

But in real life, no!