The positive sides were: the welder (it's our first blowtorch!), Freya McCloud
(I really liked the personalization that was done with LEGO city in 2020; some of the minifigs finally have names), the firefighter colored helicopter handle, the emergency motorized vehicle (the biggest of its kind we've ever built and my son likes it) and I learned how to build a pipe with several pieces.
As in many homes, the flight of our helicopter is unpredictable :) The weather conditions are however stable, the pilot always has the OK from the control tower to fly away, but sometimes he doesn't fly away or he doesn't go very far.
I tried to understand the why in order to see how I could make it fly for sure. I noticed that it is lighter than a Junior model because all its parts are not built with conventional brick. When you make it lighter, it flies better. The helicopter and the propeller weigh 24 grams, the minifig and the cabin window weigh 14 grams. Our best flights are without the minifig and the glass. The flights that are a little less amazing are the ones with the glass, but without the minifig.
Another reason that can explain the difficulty of the flights is the take-off; the helicopter has to lift itself from the handle to fly (15 mm), if it doesn't gain enough height the helicopter will stay in your hands. In order to do this, you should not be afraid to pull the plastic "cable". As my son is 3 years old, he still doesn't have the strength to pull and facilitate the takeoff. This doesn't prevent him from enjoying the propellers turning while he steers the helicopter with the handle.
In the end, maybe the set would have been better appreciated if it had had a gear mechanism that would have turned the propeller without making it fly; the handle would have had a crank that would have helped to turn the propellers.