Perspective switch:

I've banned "Real Life" for my parents because that's all they ever talk about, all day, non-stop, whenever I'm nearby, for years. To this day they still talk about my "Real Life" and compare it to theirs and play "different Real Life" imagination games with eachother.

I would rather they learn how to do important things where they use their time and mental energy effectively. I'd love for them to learn how to imagine and design and have a project come to life, and see all the steps going from nothing to a completely realized construction, from idea to reality, whatever.

I would rather they don't waste their time hammering away at mind-numbing "day jobs" where they are bogged down by having to do all the manual steps and take care of every little detail and do all the menial work.

I would rather they develop their mental abilities rather than spend all that time repeating trivial actions (like all the repetitive, non-mind-enriching wood chopping required before you can even consider talking about building a tree house in "Real Life").

What I'm trying to say:

There are many advantages to being immersed in something "that isn't the real world", and avoiding menial, repetitive, dumb, costly labor and trial-and-error are some of them.

What you're doing with your ban is simply imposing your view of the world onto them, without having any sort of context as to what their lives will be like in the future with or without this ban, and without even the context of their own minds and what minecraft truly gives them.

The reason it's all they were / are talking about is that it's a whole environment to them, and if they still talk about it it's because they still have things within that environment to talk about.

It's also important to realize that specific skills taught in childhood are almost never as important as general abilities and methodology (except for certain basic required skills like walking, eating, etc.). Learning how to analyze the flaws in a design or creation and how to come up with a more elegant, time/resource-saving solution in general is going to help your children much more over the course of their lives than learning how to specifically arrange planks of wood together so that their floor is straight and solid.

To be completely honest, I think you're making a life-changing mistake by micromanaging your children's time and activities this way. Yes, your role as parent is to guide and educate. You should inform them of dangers, and consequences, and problems, of things they want to do or are doing or are interested about. You should take action whenever it is clear and without doubt that not taking action would lead them to harm... and explain what you did and why to them later! And by later, I mean the next day, not "when you're grown up". However, the key thing to keep in mind is that each time you impose a practical rule that you came up with, you unwillingly make them more like a clone of yourself. You force their actions, and thereby their thoughts, closer to yours, while hampering their own ability to learn about the world for themselves.

My recommendation: Talk with your children about why they like minecraft, what they do in minecraft, and why you think they shouldn't spend so much time in it. And then, most importantly, listen and understand what they have to say about it. Do not dismiss their thoughts. Do not come up with reasons why their arguments are invalid, or assume you have a better picture of the situation than they do. Think about it this way: They have two fully-functional brains, and both of their brains were thinking about this issue way more than you for way longer than you did. Are you ready to claim that whatever short time you've taken to consider the issue before banning minecraft is all you need to overrule two other human beings?

You're telling your daughters, indirectly, that you can make a better decision by thinking for a few days than they can possibly make after months of being fully involved in the subject?

Because this is what they will learn. They will learn that their parent has taken decisions and imposed rules that change their lives because said parent thought about it for a little while and came up with this idea, without asking them. They will learn that you think you know best, at all times, and that you think they are incompetent, and that you think they are incapable of thinking for themselves.

At worst, they may even think themselves incapable of thinking for themselves, and give up trying, and become faceless sponges absorbing whatever your education gives them, without any more personal growth or exploration of their own.