Why frontend engineering is hard

After 8 years I know it's more than pixel-pushing.

Everyone has an opinion on the UI including your users, colleagues, and their grandmas. Only the database people know what's optimistic vs pessimistic locking, but the general population have an opinion on a button size and color, or font style and size. People will disagree and grumble about the decision.
A good frontend is like good design. It's hard to describe, yet users will know it when they see it.
A new framework or library comes out every month, especially in AI advancements. AI models can run in-browser with web-llm and web GPU. It has performance implications; the browser can crash, preventing the user from doing any work.
Many full-stack engineers started as frontend engineers who went above and beyond, but the reverse is rare. I've yet to meet a backend/devops engineer who enjoys frontend work; most avoid it like the plague.
Frontend is the top layer of a stack. The user will experience all the inefficiences/deficiencies throughout the stack, and they'll blame it on the UI.
On new projects I'm often torn between laying the foundations and prettifying the UI. Laying the foundations is critical, but people expect frontend engineers to make the UI pretty; expectation manangement is key.