Lots of websites are responsive now days but not actually properly mobile optimized. The design needs to work on the phone with responsive video and images. The hamburger menus dont work half the time. Worst of all they are too slow! Making your site fast is now one of those ranking factors you just can not ignore. Try running your site through GT Metrix then run ours and see the difference. Slow load speeds will kill you on mobile.
We have no affiliation with GT Metrix its just a useful tool.