Maybe we should try not to be quite so disparaging about instabuddies. By definition, if I'm paired up with an instabuddy I am also an instabuddy, regardless of my own self importance and feeling of superiority.
I do a lot of pickup dives with strangers. It's fairly easy to avoid the worst of the worst. After that, it's been my experience that most instabuddies have at least met the minimum standards for a dive buddy. (Keeping in mind, that a basic OW buddy is pretty much just an alternate air source.) There's only been a couple that I wouldn't dive with again.
And, there's at least one out there that'll never dive with me again...
Sometimes we're the bad instabuddy and don't even know it apparently. I got chewed out by an instabuddy once. We had met randomly at the dive site and agreed to dive solo together. That was the understanding. We were both on our own and not to rely on each other for anything. We would just be in the water doing the same dive at the same time. That was the other diver's idea, not mine. Weird, but ok, since I was going anyway.
I was wearing double 104s and, since I had planned to dive solo, I was also carrying an AL80 safety bottle, and an AL40 with O2. When I'm solo, I normally carry my safety bottle for the whole dive, but we were doing an easy circuit that I had done many times before. When we got to the junction, things were going well, instabuddy looked good in the water, so I put the unused safety bottle down for pickup on the return leg. This put a full safety bottle 500ft from the exit for our return leg, which is a great spot for a backup. On the way out, I stopped to pickup the safety bottle and buddy suddenly realizes that I hadn't been carrying it and communicates his disapproval. We do a few uncomfortable minutes of deco, with him shooting me dirty looks, while I deco on O2 and he's on back gas because he came inadequately prepared. I wait for him to finish deco and we exit together.
After the dive, instabuddy comes over and chews me out for dropping my "stage bottle." I explained that it wasn't technically a stage, I don't need a stage for that dive, and I didn't use any gas from it. And, that's what you do with stage bottles anyway, you drop them at a strategic location. Diver storms off before we can talk rationally about it. But, the funny part was this diver only had back gas and didn't take a stage, a safety bottle, or O2 on the dive at all. So, I had more gas for the dive due to larger tanks, a strategically placed safety bottle, and O2 for deco, but I was the bad diver. He's probably still telling the story about how a bad instabuddy almost killed him.
To me, having a sub-par dive buddy isn't a death sentence, and sub-par is better than not diving - most of the time anyway. Instabuddies often allow me to do dives I otherwise could not because of the no solo rules in force in most places. So when some rando asks is he can join your group, do him a favor. He most likely won't kill you.