There is no authoritative definition of DevOps, so there’s really no point in arguing that one of our definitions is wrong. I’m telling you that it is more valuable to treat ops as an engineering problem rather than “duct-tape it and keep it chugging along”. So yes, if you want to treat it as an engineering problem, you must _employ engineers_. These engineers can be former sysadmins so long as they know how (or can be trained in a reasonable timeframe) to do engineering.

WRT your “walled garden” quip, employment is about qualifications. No one is entitled to jobs for which they are not qualified, not even sysadmins. If the employer is hiring engineers and the sysadmin candidate can’t or won’t learn how to engineer, then they are not qualified.