I'd guess someone who wants to be seen as a trustworthy expert wouldn't want modern browsers to show a big "This website is insecure" landing page before people

I'd guess someone who wants to be seen as a trustworthy expert wouldn't want modern browsers to show a big "This website is insecure" landing page before people see their website. I guess this would filter non-technical people, but Let's Encrypt existence has made any argument against web certificates moot. There's no sensible reason not to.