Frontend development happens at the tail end of long pipeline of requirements gathering by product and design folks.
To meet the requirements foisted upon them, frontend devs tend to gravitate toward tools and frameworks that allow for maximum flexibility. And greater flexibility comes with greater complexity.
If you looped in frontend devs earlier in the requirements gathering phase, you might be able to (drastically) simplify a lot of the frontend work (e.g. "if we design this UI flow slightly differently it will require way less development"), but I understand this goes against most of the software development best practices which are currently en vogue.
To meet the requirements foisted upon them, frontend devs tend to gravitate toward tools and frameworks that allow for maximum flexibility. And greater flexibility comes with greater complexity.
If you looped in frontend devs earlier in the requirements gathering phase, you might be able to (drastically) simplify a lot of the frontend work (e.g. "if we design this UI flow slightly differently it will require way less development"), but I understand this goes against most of the software development best practices which are currently en vogue.