Not all receivers are created equal. A cheap dongle isn’t as good as the dedicated hardware you got, even if that hardware is old.
Maybe filtering for the dongle can help. Which dongles are you using? Not all dongles are equal.
Try this filter: Announcing the new 1090 MHz only bandpass filter!
Together with the Flightaware ProStick Plus you should get good results.
Or try a rtl-sdr blog v3 dongle with their (LNA New Product: RTL-SDR Blog 1090 MHz ADS-B LNA).
You need to enable the bias-t and that needs some software changes. If you are not comfortable with that you can also get an external bias-t.
Or you can go with this LNA, which can be supplied via USB: 1090MHz ADS-B Filtered Preamp
Looking closer at the pictures i don’t even think the performance of the AirNav receiver and the dongles differs as much as you think.
The outline you see is probably generated over 24 hours or something.
You could also check which range is possible based on terrain: