Appreciate you sharing this article, but it is very SQL specific. Rather than discussing SQL as a language / tool / concept, it talks about a single operator - I think the former would be more relevant to the programming community.

IMO posts like this are best kept within the relevant community, or programming.dev will start filling up with cross-posts.

So common in consulting. Many customers only want new things and feel like they shouldn't have to keep paying once an initial product has been delivered. But needs change, tech moves on and things need refreshing or replacing. The hardest situation is when the client has no in-house expertise so can only assume you're trying to fleece them for more money.