The big problem with many of the alternative browsers like the ones you mentioned is that they are powered by the Blink engine (it's one of the 2 options for nyxt). The overwhelming market-share of Blink and the institutional monopoly on its development is the biggest driver for introduction of anti-features like these. WEI for example, is being prototyped in it [1]. These anti-features make it into every browser that uses Blink. While some browsers like UR-browser and Brave disable many of these features, they still lend credibility to the blink engine.
We need to promote alternative web engines like Servo and libweb and browsers based on them. Many of these engines need a major push to be competent enough for daily use. Gecko is also fine - but building a new browser with it is said to be hard.
[1] https://chromium.googlesource.com/chromium/src.git/+/refs/he...