And yet it is not slow and Google is not penalting you. Out there is huge amount of mis- and disinform about PageRank and this claim is one of that category.
Otherwise optimizingquestion is really is easy. You can’t do much. On Wordpress there would be options because PHP and how sites are working but regarding an app as Discourse there isn’t similar tools.
Sure, you can start searching faster VPS and/or DNS but that’s it and you will not getting actual and real worth to your money.