Having managed agile projects at startups and big tech, there's a few problems that were common:

1) lack of customer feedback loop - agile is meant to ship features quickly to customers, get feedback, and iterate/enhance/pivot based on their feedback. Often times the projects were simply things that "had to be done" and the whole agile process was not necessary.

2) inaccurate estimation - projects would start with asking engineers to estimate "t-shirt size" efforts on user stories, and what happened in reality is the projects always ended up taking longer than expected due to unknowns, dependencies etc. I've only worked with a few senior engineers who can accurately estimate, but junior engineers starting their careers in a big company, it's a tall order to ask them to be accurate.