While true that all raids (and by extension MMO bosses in general) are just memory checks, I believe it's FFXIV's method of boss design to be why it feels like just doing a choreographed dance repeatedly. Which is not a judgement on it, that's just the games chosen design with very tight and consistent timings to boss fights. It lends itself very well to people who like optimizing their performance as after a certain point the only thing that will change is how well you personally perform in the raid. For other types of gamers though, it does get stale and this is where other MMOs, despite being a memorized dance in their own way, feel like less of a dance. I'll do the cliche and compare it to WoW where it feels more like a 'raid' as in you are raiding a bad guy's base because it's an actual dungeon rather than 4 separate square or circle rooms with a boss. This visual difference and feel is enough to hide it's basic structure for some people.
I feel like this memorization complaint is more about a general losing of interest in FFXIV's raiding itself which is valid as it is very stale and samey feeling. While the aesthetics of the current raids are great and has an in-game reason why it's just a boss fight in a square room, it's at the end of the day doing the same thing you've been doing for years. While WoW's quality feels like a rollercoaster sometimes, they have the room to throw in a lot more curve balls that spice up the different raids. I don't know how FFXIV can change this as it's kinda what they are known for and I'm not sure they want to anyway as this is just their chosen niche.