My Samsung "smart" TV is 5 years old. It's never really been all that intelligent, but it's getting slower and glitchier day by day.
I'm looking for a streaming device that runs its own apps and just sends a video feed to the TV display.
I realize this is a weird question, but if you've ever watched a movie with the audio intermittently going silent, you'll know my pain. Or how it consistently takes at least 3 seconds for the show to freeze after you've pressed pause.
Will any of the Roku devices fill my need, or will my dumb TV get in the way?
Yes, all of the roku streaming devices will do that. Find the wifi or ethernet features you want: https://www.roku.com/products/compare
Alternatively, an Apple TV, Amazon fire stick or cube, or Android TV device would work as well with slight differences in the features and apps they support.
But, just guessing - your problem may be your internet or wifi speed instead of the app the TV is running.