The Luftwaffe was doomed before the war kicked off.
It depends on what it is expected to do. Hitler and therefore attempts of invasion outside of continental Europe and you might be right, but within its immediate borders with France and Poland, you might be underestimating its capability, organisation and equipment. The Luftwaffe had some good forward thinkers, good commanders, guys like Theo Osterkamp, Albert Kesselring etc, who were sound military commanders, and let's not forget operational experience in Spain placed the Luftwaffe in a knowledgeable position regarding modern battlefield tactics. Read more below regarding equipment and capability.
But the Luftwaffe had good kit, as good as any else’s until well into the war.
Indeed it did, but its biggest advantage was how that equipment was used, which leads me to my comment above. Let's not forget that the LW had advanced navigational and bombing aids streets ahead of what the rest of the world were doing in 1939, using sextants and drift sights. Knickebein was used for precision raids during the Polish invasion and throughout European campaigns with KG 100 and the introduction of X and Y Gerat offered accuracy by night that RAF Bomber Command could only dream of. The RAF did not introduce such equipment into service on its bombers until Harris took the reins in 1942. Germany also had good size bombs and an excellent grasp of the importance of reconnaissance assets, to the extent that a third of the LW strength at the outbreak of the war was dedicated to recon duties, from long range strategic photographic recon to coast watch and weather watch flights.
The Brits bang on about their recon assets during the war, which were obviously extensive, but before the war, the Germans were out-Sidney Cottoning Sidney Cotton and had a far bigger dedicated aerial reconnaissance apparatus than the RAF. The Abwehr had its own strategic recon operation with surplus LW aircraft being used for spy flights across Europe, Lufthansa had cameras mounted in many of its international airliners at the behest of the Abwehr. While Cotton was pootling about with his Lockheed of his own accord and his efforts refused by the RAF (the Royal Navy gladly accepted Cotton's offer), the German state-owned intel services were doing exactly the same as he was, using both civil and Luftwaffe equipment. In this respect, the Germans, via the Luftwaffe were far better served regarding battlefield and strategic intel, better than the RAF, the Armee de l'Air and virtually every other air force in the world.
Great War air force? Far from it. The LW had the potential and the minds to be the most efficient in the world at particular disciplines.