Server side rendered pages and SEO support will be introduced along with Mendix 5.
Howto - Search engine friendly Mendix App
MxBlog is a mendix app, so to proof that this works: Google: Mendix SEO Crawlable
By nature Mendix apps are not public sites to be searched and found. That's why the robots.txt is preventing the crawlers to index your site.
Not being complete some thoughts from my side: