The important part is, that the greats never were okay with just 80%. Their goal is usually to make the best work they can and that means improving on things they have previously done. That doesn't mean the project needs more work or resources. It means it makes best use of the work and resources available while delivering something that satisfies the masters quality standards.
Also: In some cases 80/20 mediocrity does in fact not cut it and it is just an excuse to do less work and not to think hard about things.
I'm a perfectionist miniature painter by hobby. I love the stories floating around about how quantity can lead to quality (photography, pottery): https://austinkleon.com/2020/12/10/quantity-leads-to-quality...
In most of my hobbies I feel like my growth and talent is limited by lack of volume, not my care or attention to detail. It's hard to let go and use one color instead of three, or not fix a flaw in model part nobody will ever see. I'm sure other people have the opposite challenge.
Coincidentally I teach (medialab) at one of the most recognized art universities in Europe and have a MA of fine arts and my mother is a painter. In my judgement the most overlooked (or most underrated) skill when it comes to painting is perception. Being a good painter aside from the manual skill has a lot to do with seeing or being able to see, even if you're not doing figurative paintings.
Painting more and more different things can be a good way to raise your own perception skills. It is also important to revisit old works occasionally. Ideally you will immediately see what was wring (or good) with them, something you may have not perceived back when you did it. This is proof that you leveled up.
How do you like those 80% Boeing aircraft with optional parts that may or may not come away in flight?