Braking issue?- soft...too soft?

I recently (~1400 miles ago) got my brake system taken care of- new rotors, brakes, flushed lines, etc. However, I noticed that my brakes felt soft. The pedal would go a lot lower and take considerably more force to stop. It wasn't going to the floor, but still pretty low (maybe 4" from the floor). They were still responsive, but just far less so than my older brakes.

So, I figured I may have air in the line and the flush was bad. I had it reflushed, but still the issue remained.

My brakes feel soft sometimes when in park and the car is off and hard other times. In park, I can pump the pedal to hardness without issue.

While driving, after braking a number of times, the pedal hardens a bit and becomes more responsive. It stays harder at that point (but not overly stiff). I don't smell brake fluid or see any leaking, as if a caliper were leaking or anything.

I'm not getting grinding, squeaking when braking, or anything like that. The pedal just feels soft..

Also, to note, the weight of my foot resting on the brake (heel on floor, foot on pedal) isn't enough to make the pedal sink any more than maybe less than an inch (when soft).

Could I be just used to my older, worn down and sticky, brakes?

Maybe these need time to wear in? I mostly (like 90%) drive interstate. So, breaking is not frequent.

Could the mechanic have just gone with a different type of pad, and thus it feels different?

Any tips/advice is greatly appreciated.

UPDATE Master cylinder was fine. Apparently my rear brakes were not aligned. So, I was basically only braking with the front.