While all these cards are powerful, a plethora of colorless lands (Myriad Landscape, Ghost Quarter, Homeward Path, etc.) and utility cards (more Modular creatures like Arcbound Reclaimer & Arcbound Overseer, Liquimetal Coating to help your non-artifact creatures pick up +1/+1 counters from fallen Modular creatures, and Contagion Clasp for repeatable Proliferate) can readily fill the gaps
Market dynamics are another complex element of the equation
Whenever a face-down creature you control dies, return it to the battlefield face down under its owner's control if it's a permanent card, then turn it face up
This may seem like an odd choice, but given how good Dragons can be in Commander, its hard not to look to this as one of the best options for destroying everything else if youre a big fan of scales, fire, and generally being bigger than everything else
Usually, its the ultra-rare cards that make headlines