Remember the "Safari is the new IE" narrative? Just because Safari doesn't support some API doesn't make it IE, IE wasn't an inferior browser at the beginning either. What made IE the IE everyone hates was its departure from standards(?) and enforcing its own vision of the web thanks to its enormous market share. On IE's case, MS probably stagnated it to prevent competition against its desktop Apps business and on Go…
Safari already implements Manifest V3 (it never had anything else to block ads) and DRM. So what the heck are you talking about? Safari is leading the charge on all those hostile changes. (Not to mention all the other ways how they undermine the web, like refusing to properly support PWAs and forcing you to go through Apple reviewed process for apps.) This strange narative how Safari (the only browser you're ever all…
This isn't entirely accurate. Confusion on the issue abounds.
From 2010 to 2019, the safariextz format had support for webRequest BlockingResponse https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web... and indeed there was a Safari version of uBlock Origin. This was eliminated in Safari version 13.
The "newer" (2015) Safari content blocker API is similar to Chrome's declarativeNetRequest. However, Manifest V3 is far broader than just eliminating webRequest BlockingResponse, though that's what people tend to focus on. For example, there are strict limits on script execution that also cause problems for userscript extensions.
Safari web extensions (2020) will continue to support Manifest V2, albeit without webRequest BlockingResponse, which Safari web extensions never supported. Apple is in the process of adding MV3 support to Safari web extensions without deprecating MV2 (just like Firefox).
In a sense, Manifest V3 and delcarativeNetRequest are separate issues. After all, delcarativeNetRequest is also supported in Chrome MV2. Chrome took the "opportunity" to eliminate webRequest BlockingResponse in MV3. Safari took the opportunity to eliminate BlockingResponse much earlier. But MV3 could have supported BlockingResponse if Google had wanted; there's nothing inherent to MV3 that precludes the API, other than an arbitrary decision.