It's been there for quite a while now. Don't know how much more time the developers need to get it fully functional.
It is fully functional. Many of us have been using it for several years now but that doesn't mean it isn't still in an early stage of development with plenty of room to grow.Plus it is responsible for securing millions of dollars worth of value; such things should not be rushed. Centralized shitcoins regularly have critical bugs which result in huge losses - bitcoin is different.
Lightning does simply solve what the core developers do not want to do at this point. As soon as Bitcoin gets the correct update all the lightning development will be for nothing.
Block size in bitcoin has already been increased from 1 MB to 4MB. There are very good reasons to not just endlessly increase block size, but if large blocks is what you want then there are a selection of shitcoin forks you can choose from. The fact that every one of them is constantly losing more and more value against bitcoin should tell you something though. 