I'd be the contrarian here and say it's easy to make 300k+ with molar endo and crowns alone. The reason I didn't include implants is because implants take a bit longer to monetize and failure with a full arch implant prosthetic results in significant losses due to waste of time and lab costs. Molar endo is an important skill to learn, since molars tend to need root canals more than premolars/anteriors (due to first molars being some of the first permanents we get, poor access to oral hygiene, increased masticatory forces, etc...). Molar endo, buildup, crowns (and sometimes crown lengthening) go hand in hand and unlock a whole new level of productivity besides just picking one or two of the three/four procedures. Flapless crown lengthening makes crown lengthening much faster and more efficient, especially with the use of hard tissue lasers if bleeding needs to be at a minimum. If you learn those(RCTBUCrn + CL), you will be a single tooth specialist (and if you want to go further down the line, learn retreatment, apico, intentional replant, ext + graft + implant, and explant/reimplant). That way, you can take care of any single tooth/space in any stage of its lifecycle.
It's a catch-22 situation here. If you don't do them, you'll never learn how to get better. However, if you don't do it well, you increase your potential future liabilities depending on statute of limitations/occurrence. I think it's important to actively learn from every procedure you perform, especially when you're in the starting phases of your career. Unfortunately, molar endo usually accompanies a crown and if you refer the molar endo, what's the probability you'll get your crown anytime soon? The better line of thinking is get better at procedures that are related to each other.... i.e RCTBUCrn, Ortho/Veneers for cosmetic driven practices, implant/GBR/soft tissue augmentation for implant driven practices, etc... There's working sets of procedures that can be done productively and decreased aggregate appointment time for increased productivity.