I like MaterializeCSS but the way forms are styled isn’t compatible with legacy forms.

If you are using Configurable Engine, checkboxes in admin page are broken. You can fix it by creating app/views/admin/configurables/show.html.erb with this code :

<div class='configurable-container'>
  <div class="header">
    <h2>Config</h2>
  </div>

  <div class="configurable-options card-panel">
    <%= form_tag(admin_configurable_path, :method => :put) do -%>
        <%- @keys.each do |key| -%>
            <%- options = Configurable.defaults[key] -%>
            <div class="#{options[:type] = 'boolean' ? '' : 'input-field'}">
              <%- if options[:type] != 'boolean' %>
                  <%= label_tag key, options[:name] %>
              <%- end -%>
              <%- if options[:type] == 'boolean' %>
                  <%= check_box_tag key, "1", Configurable.send(key) %>
                  <%= label_tag key, options[:name] %>
              <%- elsif options[:type] == 'password' -%>
                  <%= password_field_tag key, Configurable.send(key) %>
              <%- elsif options[:type] == 'text' -%>
                  <%= text_area_tag key, Configurable.send(key) %>
              <%- elsif options[:type] == 'list' -%>
                  <%= text_area_tag key, Configurable.serialized_value(key) -%>
              <%- else -%>
                  <%= text_field_tag key, Configurable.send(key) %>
              <%- end -%>
            </div>
        <%- end -%>
        <br/>
        <%= submit_tag 'Save', :class => "waves-effect waves-light btn"%>
    <%- end -%>
  </div>
</div>

Or you can use my fork of the gem compatible with materialize.