While I'm not gonna argue the merits of GPL—it is technically restricting modification, even if there is no practical difference for those only interested in adding/removing functionality—I disagree with the assessment that using the GPL causes harm to the users.

The reasoning seems to be that a 3rd party's refusal to use the software because of the license, and suvsequent use of a shittier product is somehow the (hypothetical GPL-using) OpenSSH dev's fault.

The problem is that accepting the premise that the devs are responsible for what people who choose to not use their software do entails that they are then responsible for everyone who uses any type of software tangentially related to OpenSSH's functionality. It also means that it's their fault for whatever consequences of using the licenses they currently do, which inevitably drive some people away for various reasons. It also means any potential license (or even lack thereof) is open to the same criticism.