Yes, everything in State of Decay 2 is a slow build-up, a careful logistical stew of having the right survivors with useful skills, the right size base with proper construction, outposts and mods, the right weapons, vehicles and equipment, and making friends with the right enclaves (to get their bonuses). As these things fall into place you can tackle tougher and tougher challenges. That first plague heart may be doable with you, your follower and a member of the neighboring enclave hacking at it with mower blade swords, but they’re going to require more preparation and better equipment as you progress. (I prefer pipe bombs myself…through a nearby window is best.)
For infestations your vehicle is often your best weapon. Pull up in front of the house/building and honk the horn a couple of times. Zoms will start spilling out the windows and busting through the doors, and you can mow them down with your car doors open. When the screamers finally come out you know you’ve reached the end of the infestation. Take 'em out with a headshot and infestation cleared.