I really disliked my Chromecast...despite being able to output 4k, the OS was sluggish and it barely had storage to hold the streaming apps I was interested in using. I ditched it for the Apple4K.
I didn't even know you could install apps onto a Chromecast. I'm not sure why you'd need to though, because phone apps can "cast" to it.
IMO this is a part of the reason why they're dropping the Chromecast branding. The product is very different from the original Chromecast streaming stick. It is now mostly a cheap Google TV device.
I also quickly ditched mine. I mean it worked sorta fine - but the usability was absolutely terrible. Often apps lost connection with it so any requests to pause or resume the media was several seconds delayed. If I got a phone call I often wanted a quick way to pause my media but chromecast made this super inconvenient, slow and stressful when the phone is blurting out it's ringtone.
App support was also spotty at best.
In the end I realized that since I've already chosen between a rock and a hard place (went with the Apple ecosystem), I could just screenshare using an old Apple TV. This ended up working much better in practice (although lower quality video stream) than Chromecast. Today I don't cast much video anymore for some reason, not really sure why. I have an Apple TV 4K and just mostly use the native apps from various services. Having a remote to a system that is completely detached from your phone is much nicer usability wise IMHO.