I disagree.
An engineer with soft skills, but no hard skills, isn't an engineer – but their soft skills may be usable elsewhere. (I find that engineering managers need to have a decent amount of engineering skill to be at all effective)
An engineer with hard skills, but no soft skills, is somewhere between unproductive and an active menace. The bare minimum soft skill is the ability to work effectively with others in a team. Someone who lacks this skill contributes more negative value, by harming the operation of the rest of the team, than any one person is able to create, no matter how good they are. And a system built by one person in angry isolation (which is where people quickly end up if they lack those skills) is a disaster from other perspectives: for example, production maintenance and operations, where ultimately only one person understands what they've built.
An engineer with enough hard skills to function in a team, but only that, is a net positive, but I'd hesitate to describe them as "solid" – rather, I'd say that gets them to be an effective journeyman, but means they'll never be able to lead anything, even something small.
Conversely, the "engineer" with lots of soft skills but minimal hard skills can be a manager – but not of anything too complex. Again, their career is permanently limited.
So there's a real law of the minimum at play here. But notably, the place you drop to at zero soft skills is way worse than the place you drop to at zero hard skills. The latter, you can find a use for; the former, you need to get out of your organization as quickly as possible, because they do active damage every day.