DIR extends beyond the equipment configuration and some of the procedures but also into the mindset of the 'team'. DIR is what it is, and for anything different, it isn't DIR. Diving solo, failing to discuss the dive plan, goals and expectations of the team;separating and not looking for teammate and so on simply are not DIR.
That said, I dive with non-DIR people all the time and always discuss certain things. Usually, gas management, depth constraints, the dive can be aborted anytime for no reason at all, keep within sight of each other and effective response distances (usually 10-15 feet maximum) except when low viz or high current then closer, here's how I deploy the long hose in case of emergency, and what the lost buddy procedures will be, etc. Whether the person understands and puts that into practice or not during the dive is another situation. Usually they'll understand things like turn pressure and staying close in case of emergency and lost buddy procedures and anything beyond that would take more dives as a team to absorb.
If they race out of sight it is still a good idea to try to find them. I had that happen once a while back and the person was stuck in kelp in a severe panic. Because me and my remaining buddy looked and found him, we were able to avert something catastrophic. Whether I'm DIR or not, or whether the team is doing a DIR dive or not, is besides the point. I'm also an insured dive pro and do not want to be successfully sued for any kind of negligence so I cover my bases, When I insta-bud I rarely discuss that I'm DIR at all but I do instigate communication and try to get on the same page with them (that is usually how it will be, I doubt any non-DIR would easily get completely on the same page as me). And do you know what? 98% of the time I enjoy the dives and the company. Only a very few times have I regretting doing THAT dive with THAT person. But my decision to dive with the person starts long before the dive. Aborting the dive at any time means can include before the dive even begins.
Sometimes people size me up. Just a few weeks ago I instanted with someone in Monterey and they (non-DIR) sized me up and then we had a very wonderful dive together.
If you are comfy with non DIR (you can still be DIR -- though the team isn't) then dive with the people. If you aren't, then don't. Just don't call it DIR when it isn't. Lack of communication, planning, and lost buddy protocol is not DIR by any stretch of the imagination.