I currently have a Nvidia Shield that I bought from Amazon back in November 2019 that I overpaid for ($299) and I haven't even used the controller once. I'm having several issues with a few apps and the only way to get it to back working is to restart the device. I'm sure it's the device (it's up to date) and not the apps or the WiFi because I have an older smart TV (Sony that I bought new 6ish years ago now) that when using the same apps it doesn't do this. It's just slow to load up those apps and to navigate through them (which is why I bought the Shield and it was amazing at first before these issues).
Football is starting and I don't want to have to restart the Shield through the games but at the same time I don't want to spend a ton of money to have something be flakey like the Shield. I have a Roku stick on my bedroom TV as it's not a smart TV and it's sluggish as well, not as bad as the main Sony TV but enough so that I want something else.
Have you tried a factory reset on the shield? It's still considered to best android tv box, so i would be hesitant to recommend another one with the expectation that it will be better than the shield.
Chromecast with google TV may be a good option for you depending on what your setup is. It's missing some features like usb and ethernet, so make sure it has everything you need first. All that being said, I don't think it's better than the shield, but if you don't need some of the shields extra features it would be hard to distinguish the two.
If you want the best android TV experience, a new shield might be your best bet, assuming you can't fix the one you have now.