so you bought a device with out looking into the back ground of its history, neither done any research on the current model?
Now you've bought an ATV 4 and find it rubbish? So because you can't do the above that means its rubbish. Yes there are flaws with this modal but as stated over many threads and posts it will get better in time (new apps, new software updates) You really need to play around with it more and learn about it rather then just saying youTube wont let me search, its crap...
Maybe the problem is the YouTube App? Google is not famous for its prowess at UI design.