Why is my iPad stuck on iOS 10.3.3

So, that’s an iPad 4th generation, so yes, it cannot run anything newer. iOS 11 and later requires a 64 bit processor, iPadOS 13 or later requires at least 2gb RAM, which are hardware requirements that your iPad doesn’t meet.

Because it is too old to run anything newer, because it is obsolete, and most likely came out approaching a decade ago. If you let us know the exact iPad model, we can confirm this for you.