If this is a professional gig, then IMHO your first priority is to make your client happy. It is not to have fun on their dollar. It is not to improve your portfolio on their dollar. It is to produce work that meets their needs.
So, if they have explicit requirements for the project, then that is your spec. By all means offer sound professional advice, and privately hope they accept your recommendations because you think the results will be better for them in the end. But as long as they are paying the bill, they get the final word.
If you aren’t happy to work for them on those terms, I think you should politely decline the gig, and ideally recommend someone else they could approach instead who might be a better partner for them to work with on the project.
If this is a professional gig, then IMHO your first priority is to make your client happy. It is not to have fun on their dollar. It is not to improve your portfolio on their dollar. It is to produce work that meets their needs.
So, if they have explicit requirements for the project, then that is your spec. By all means offer sound professional advice, and privately hope they accept your recommendations because you think the results will be better for them in the end. But as long as they are paying the bill, they get the final word.
If you aren’t happy to work for them on those terms, I think you should politely decline the gig, and ideally recommend someone else they could approach instead who might be a better partner for them to work with on the project.