"I liked the idea of carbon offsets, until I tried to explain it as if its aim were something it isn't. Then I found out that it was badly suited to the goal I imagined."

As I remember the aim from when the carbon emission quotas were proposed and introduced, offset trading was meant purely as a transition mechanism, and wasn't intended to have any effect on the long-term situation afterwards. All the carbon emitters at the time got large quotas valid for a long time, so large that noone protested much. Later, the idea was that the quotas should be reduced and then lead to quotas being sold sale and emitters closing down.

This what happens now, as I see it. I read about a company recently that decided to replace its vehicle park with zero emission vehicles, but gradually, and buy carbon offsets from someone to compensate for the old vehicles. So someone with one of those old quotas shuts down a polluting plant a few years earlier than necessary and sells an offset, someone gets to brag about zero carbon vehicles quite soon in the process of replacing their vehicles. The offsets mean that both of them can get a PR win, and arguably push both of them stop emitting carbon a little earlier than would otherwise be the case. It's a win-win effect on the transition and has nothing to do with anything other than the transition.