Haven't we had the technology to remove minion block for a while?

Just Ghost everyone. It's that simple.

Obviously, there are certain items (), abilities ( passive), and even a summoner spell that specifically lets you walk through other units, but why isn't it just put on everyone?

The reason that minion block is still in the game is because Riot had problems in the past with removing minion block, namely that skillshot hitboxes acted weird. I believe they called it a technology issue, but I'm not sure.

But Ghosting has been in the game for a while now, and it's not a buggy mechanic, so why doesn't every champion have it at this point?

I've seen defenses in the past for keeping minion block, like that it adds an extra layer of strategy to the game. But it takes away from the game more than it adds because of how unpredictable it is. You can ask many, many people about a minion block experience and the majority of the time they will tell you it screwed them over in a way they couldn't predict.

Thank you for reading.