No. These are printed plastic advertisements delivered via the postal service. (Other companies might purchase small mini catalogs/coupon books, colorful envelopes, or eye-catching postcards for their mail-based advertisements.) These mailers are sent to many people. Most people refer to these mailers as "junk mail."
Spectrum is very bad about sending lots of these, as OP has shared.
They likely had Spectrum as an Internet provider, but left them for a better one. Spectrum sends lots of spam in an attempt to bring them back like an ex-lover trying to win them back.