You're right. But I still think I would buy my kid their own iPad even if my iPhone/iPad had a kid mode. My kid has their own iPad and I still find times when it would be ideal to give them access to the basic features on my phone/ipad. Frankly, if iOS just added the ability to password protect any app then that would be good enough, and it would be useful for more than kids... hand you phone to a coworker or relative to look at photos they can't accidentally/intentionally hop over to your email.
[0] https://support.google.com/nexus/answer/6118421?hl=en This link is for Nexus, but I think it's included in all version of Android since 5.0 Lollipop.
Once upon a time, kids went to school without phones, so it is possible...
It has a lot of options, but probably not enough (like restricting specific apps.) You can however set to allow only apps rated "4+ years, 6+, etc.
Time limitation is possible too, via "Settings -> Accessibility -> Guided Access".
The funny thing is, Apple didn't want to call their computer a "PC", but their smartphone is more a personal computer than any other brand.
Why doesn‘t the iPad have this sort of multi-user mode? An iPad is the perfect device for sharing. But no, if you don‘t want your kids to read your emails, you need to buy them their own iPad.