Restricting webRequestBlocking (but it's not going away, just needs a policy extension) and synchronous executeScript did in practice make adblockers unreliable though.. I partially worked it around by using a custom extension that uses the recent userScripts API..
BTW, it's not possible to inject scripts to workers like a ServiceWorker or to replace it's content (DNR let's you redirect but this redirect breaks SW origin + it's visible when you disallow redirects), but MV2 was no better, chrome extensions never had advanced capabilities for ad blocking, a bug about not being able to access POST data via webRequest was open for 10+ years and will probably never be fixed.
But still, firefox is not the alternative, even WebKit is much better.