Well many of those aren’t even Deus ex machinas… Also, Harry never was a talented wizard in terms of gifts other than defence against dark arts, like Hermione for example was a better wizard when it comes to spells in general. That’s why he could learn the patronus charm rather quickly, since it was in his area of specialty.
Also, Dumbledore never really taught Harry much (in fighting or spells), he guided him. So it makes sense that Harry wasn’t overpowered even tho he was the ”special one” and had the greatest wixard of all time as his mentor. Harry’s best qualities were his defence against dark arts spells and his bravery (or rather, stubborness).
And there’s no way Dumbledore could’ve defeated Voldemort by himself. In a fair 1v1 probably, but Dumbledore was already past his prime and Voldemort was immortal thanks to his Horcruxes, so in a stretched out battle until death Dumbledore would’ve definitely lost after fatigue kicking in since he was so old. In order to take down Voldemort for good, Harry needed the help of basically all his friends, but the most crucial were Dumbledore and Snape who did so much groundwork and gave their lives for it to be possible.
But I do agree HP has plot holes and plot conveniences, but didn’t bother me too much. I mean pretty much every franchise has those.
.
