They aren't adding new story with these patches, rather expanding on what they have already told in the game. Consider it extended director's cut and then tell me how is it bad?
If you buy games at launch, no matter what they are, you will always get an incomplete package with bugs, performance issues and lacking QoL changes. This applies to majority of the games releasing this generation and if a developer decides to support their game post-launch, why do people start calling it incomplete. I will never understand it.
Bloodborne, which is hailed as one of the best games, was released with issues that affected it seriously like the minute long load times, bugs that could break the game rendering progress useless and more. They were patched post-launch but if you would have played the game at launch, you would have a much terrible experience compared to the late adopters. The same applies to Witcher 3 and it will be the case for FFXV as well.
However, if you enjoyed what you played, then I don't see why additional post-launch support will make your original experience bitter. Unless you have prophecy skills to see how the game gets supports after launch. It's a shame that FFXIV gets excused because it's an 'MMO' even though it didn't reach its current state until tons of patches after launch. So the original users who bought the game at launch essentially played an early access version of it.