Extremely slow loading by certain apps

I I just switched to an Xfinity plan on my Android phone last week.  Ever since I switched, apps like Outlook, Substack, etc., that are feeds from some platform can take up to 5 minutes to load.  For example, it can take up to five minutes to populate the content of a text email when I try to open individual emails in Outlook.  Is this true in general with Xfinity phone plans or are there settings to be set to overcome this?  It is definitely making me rethink whether switching to an Xfinity plan is worth it.