Over the last 13 years or so, the Marvel Cinematic Universe has grown from a then-relatively novel experiment to the most successful film franchise in cinematic history. Its runaway success inspired other studios to take a crack at creating their own cinematic universe, but none of them have achieved the combination of financial success and critical/audience goodwill that the MCU has.
The failings of other studios are is due to factors such as ignoring the source material's strengths, rushing to get to the crossover film and adopting a reactionary approach that shows a lack of planning on the studios' part. Studio executives are largely to blame for these issues, as their priorities are more commercially minded than achieving any kind of artistic integrity (see: the theatrical cut of Justice League, Morbius and the Dark Universe for starters).
That said, the MCU is not without issues of its own. Despite maintaining a largely consistent string of quality across its films, there have been a few hiccups here and there that are indicative of the fact that the franchise is not infallible. After all, it is a commercial franchise and its desire to maintain its consistency can get in the way of successful experimentation.
Although it has been able to succeed despite these issues, there is the nagging feeling that the MCU may have been a different, somewhat more interesting beast if the higher ups had not gotten their way.
10. Black Panther's Botched Third Act Battle
Although Black Panther was lauded for its well-realized characters, visual splendor (in terms of its production design and costumes) and storytelling, it is near-universally agreed that its third act left a lot to be desired. The VFX work needed to realize the sequence was evidently rushed and this led to the action feeling artificial and lacking any impact.
It has been recently revealed by Todd Sheridan Perry, one of the movie's VFX artists, that the studio mandated release date of February 2018 and the time constraints it presented were not enough for the digital artists to effectively render the set piece and give it the authenticity it deserved.
To its credit, Marvel Studios acknowledged the challenges at play and sourced an additional effects house to ease the ambitious process. Unfortunately the rendering systems used in the houses are vastly different from one another and would not mesh well in the best of circumstances, let alone this limited timeframe.
Additionally, there were plans for expanding the set piece involving other tribes and a greater scope but the limited timeframe and incompatible systems meant that the film was stripped of elements that could have elevated a so-so third act in an otherwise good film.