I had the same issue on my Galaxy S5 smartphone as well as on a Windows 7 laptop. Evernote worked fine for months and then the app became very sluggish a few months ago. I edit some notes on my phone but that became nearly impossible with the sluggish response. I would have to wait for 10 seconds or more for each word or character to register. It was impossible to type even short phrases.
I've read elsewhere that formatted text can cause this lag. Things as basic as bold type, and colored fonts. Those are the only extra formatting that I've added to any notes. No web clips or media files.