The soft obligation to use HTTPS these days has deranked old HTTP-only websites in search, making them hard to find. These websites are also "defaced" with browser warnings or some subresources may not load at all.
Embedded maps no longer work, since Google regularly breaks their API.
Facebook login or other FB plugins no longer work, since it needs a yearly checkup of your account and there's the new requirement of needing to have a privacy policy.
Those are just some examples of websites partially breaking through no fault of its creator, if you'd agree that the web should be backwards-compatible.