You may be doing more than you think. Actifit seems to calculate a bit differently, and you probably don’t have your phone on you tracking absolutely everything in a given day. I think their app will improve in time.
My Actifit today is just over 6k, but my step count through my health app/ Apple Watch, which I trust more is just over 10k!
Either way, 5k is great for average daily activity. There are some jobs and folks that are a lot more sedentary. Hell, I just looked back at my last day off and it was 600 steps! 😂 Lazy ass day for me, + sitting at drafting table & computer instead of on my feet at work.
For regular 10k I think you need to work in a big space with a lot of movement, or consciously add in an evening walk, treadmill run, etc.