@sharkbait13 I am jacked and have not done BB squat, deadlift, bench, or BB OHP for a few years. I started off doing all of those though and I did them for 5-10 years.
In order to pivot like the people you are talking about, you have to build your base first. You get strong as you can for the first 3-8 years using these basic movements and eventually you will just learn that you need specific movements like squat, hip hinge, vertical pull, horizontal pull, vertical push, and a horizontal push. You will learn how to effectively do any exercise that is not these exact BB workouts while still hitting all the muscle groups.
Functional fitness is strength training but also cardio. You can break these two categories down even further the more you optimize.
Keep it simple, build your strength up for a few years my friend. Optimize the time you spend in the gym instead of wasting it. You can retain your cardio.
BTW Dr. Peter Attia is a leader in this "functional fitness" sphere and even he mentions the basics.