Actually the Haut-Karabakh war demonstrates that the heavy use of loitering munitions (weaponized drones) by the Azerbaijani army was decisive because the Armenian army was not equiped with counter-drone systems (RF jamming, GNSS jamming, laser...).
The lessons learnt, from my point of view, are:
1. It shows how efficient and lethal are the loitering munitions - for a very good introduction about loitering munition: https://nationalinterest.org/blog/buzz/why-loitering-munitions-are-newest-and-deadliest-threat-81241;
2. It convinced many countries to allow budget to develop rapidly very efficient counter-drones systems ;
3. Although not really used in this war, swarm of drones is the next real threat for conventional armies. Countries like Turkey, China and Russia are actively developing the technologies required to deploy swarm of drones;
4. Autonomous (weaponized) drones are coming as well. It means that such drones will be able to achieve their mission even though the communication are jammed. It means that these drones will be more difficult to destroy that the "conventional" (loitering) munitions which are remotely operated.