It's good to see more people developing in Elixir.
But having said that, I'm against server-side forms. I feel client side frameworks like vue.js completely alleviates the need for server-side form objects and does a lot more. Server-side forms at times can be a real pita to work with.
server side validation (which is indeed requried) != forms.
also, Ecto does really good job with changesets, including hard-to-do-right pieces like "uniqueness"
IMHO, reusable server side validation == forms without widgets (and widgets are nice to have if one feels that JS is unnecessarily complicating what could be a simple static HTML form).