Steve_K_Excel
Thank you for the explaining the challenges involved with applying Conditional Formatting to Named Ranges. As a developer myself, I certainly understand them. But as PeterBartholomew1 said, CF does still seem stuck in time.
You mention that performance must be taken into account. But performance doesn't necessarily apply only to the application. Users personal performance should also be taken into consideration. I have personally spent many hours correcting CF rules because named ranges are not supported. In some cases, I've even written VBA to wipeout and redo the rules for a page. But that's way beyond the average users abilities (users in this forum excepted).
As for backward compatibility, consideration needs to be given to todays world of subscription services. This means that old versions of Excel, especially in the business world, are slowly but surely getting fewer and far between. Just like old versions of Windows, old version of Excel need to be deprecated. If that means loosing some backward compatibility with old versions, then that's something the legacy users should need to deal with. As it is, old versions of Excel already cause problems with new, unsupported functions. As much as I hate to say it, it's one more reason to promote subscription services.