Unless you're a static content site that is using TLS just to be an Internet Good Citizen to prevent passive traffic analysis, you absolutely should have HSTS enabled; it's not really a judgement call. Without HSTS, you almost might as well not do TLS at all; HSTS prevents a serious, effective, and easy attack.

By way of comparison, it has never been a good idea to default to HPKP. Privacy-sensitive sites should be pinned, and if you can't safely manage pinning, that's a pretty good sign that you're not mature enough to engineer privacy for the site either, so I don't have that much sympathy for the argument that it's a foot cannon (this is, of course, very easy for me to say). But if you're just selling coffee beans or scheduling laundry pickups, PKP has always been a very bad idea for you.

Why does being a static content site mean you should not enable HSTS? If anything, HSTS is easiest to roll out for static content sites.

One primary example would be sites like software repository mirrors, where the majority of content is signed already, and serving them over HTTPS provides negligible benefit to your users (other than the slight confidentiality increase in that an adversary wouldn't know what exactly you downloaded), as opposed to a site serving active content like JavaScript and CSS, which can have disastrous results to the users if an adversary tampers with them.

The latter example is where HSTS becomes an invaluable tool, since now the only way those resources could be delivered is through a trusted channel, verified by the PKI. The same value is not there for a software mirror, because of the other security safeguards already implemented, removing the need to trust the delivery channel. That said, most still do server their content over HTTPS as well.

The browser will completely block access to the site on any certificate issue. In practical terms, HSTS removes the "ignore certificate error" button that everyone got used to click.

It will backfire when the certificate expires, when some clients don't recognize the CA chain, when domains or subdomains don't match the certificate.