Alden looks nothing like Ford.
Don't forget that Alden was Phil Lord and Chris Miller's choice. In fact, PL&CM have publicly stated that they tested Alden first, and had already decided they liked him the best, prior to testing any of the other 3,000 actors.
Don't get me wrong, I think Alden, as a professional actor, has the ability to act like Han, but there are plenty of other actors that naturally look and sound more like Harrison/Han than Alden does.