If an architect that hasn't coded in 5 years or more dictates technological decisions to you, when they are out of touch of current best practices, how do you bridge that gap?

Building codes change. Architects are required to design buildings according to the new codes. There is no such thing in software.

When I first started in industry, storing plaintext passwords in the database was what everyone did. We have moved on from that. I've worked on j2ee web apps, where the EJB tier absolutely had to be on a separate server or servers. Times have moved on from there. I've met very few "software architects" that have kept current without writing code at least 5-10% of their job.