Spectrum is requesting I order a Xumo Stream Box

Yup - - Spectrum is looking for more revenue!  Renting Xumo Box's is one way.  Forcing those with TV's 8 years old or older to get them is a way to make that happen faster.  Outside of that, there is no real reason to disable the app on the older models.  Spectrum hasn't updated their app in years, And they aren't doing it now.  Don't get a Xumo Box... Use your Roku - at least until Spectrum decides to disable their app on it as well to sell their box.