I'm using an iphone 8. Certainly not the newest or fastest phone, but I've been using EN on it for a few years, and this problem with EN only started in the last 3-6 months, so I don't think the phone itself is the issue.
Most of the time I'm on my home wifi, where I have a strong signal and a fast connection. For example, I just ran a speedtest and got 500+ Mbps down and 300+ Mbps up. I then went into Evernote, made an edit to a note, saved and closed the note, and it took 39 seconds to sync.
Thanks for your help!