There have been reports that Marvel Studios has been abusing their power over several VFX studios and artists working on their movies and shows.
Key complains from the report mention them being overworked/crunch time, being underpaid, constantly telling them to scrap and redo VFX work at the last minute even after considerable amount of time/effort had been put into the effects, and also threatening to blacklist artists from the industry f they speak out about this.
That would explain why a lot of people are noticing that the special effects for reent Marvel projects have been lacking compared to prevous works.