Yes, security has downsides, but in my opinion those downsides are well worth it for the benefits.
If a website puts out an HSTS header, they are telling the browser they need a higher bar of security than regular SSL.
Chrome: type badidea
Visit customers that try to MITM you, get protected. That is, in fact, the point.
Similarly: I have a static site (no tracking, no PIIs) that's currently hosted on a friend's VPS. HTTPS is out, because they're already using it for something else, and Apache can't know which vhost the user is requesting in time to present appropriate certificate. Maybe there's a workaround for that, but neither I nor my friend know of any, we've both already spent few hours looking, and I do not feel like spending even more time figuring out, or moving it to a dedicated VPS with its own IP.
Basically, on the one hand I'm all happy. On the other hand, I totally do not want to do the work.
And beyond that, all the extra complexity introduced everywhere that you mention, and that I also had happen to me.
Support is at about 97.9% globally: https://caniuse.com/#search=SNI - Effectively every browser released since 2010 plus IE 7 and 8 on Vista.
Computer goes out of sync with some kind of cache server, welcome to HSTS errors and not able to surf to any site with cached content there.
Visit customers that have self signed certificates on their guest network, hello LTE to be able to do anything.