As I think about the fight more and more, I feel it works well overall with what will need to happen as time goes on.
First part is that Luffy still has a long ways to go, and we have a tangible aspect to see where he can grow. Some argue that in that short amount of time he should've gotten the side affects away, but that seems to be a bad view to take. Who knows how long it took to take away the downsides of Gear 2 and 3, which at the time were already bad enough. This is the worst one, where he can't make any movements for 10 whole minutes. Who knows how bad it was before this, and how long it took to achieve this form. The other problem is it's not just using his devil fruit to increase is ability, but also using haki/will power. I've seen comments about how Luffy should be easily able to continue because of the will we've seen from him. If we go by what we saw from Marine Ford, he eventually lost all his will. In this case, he was pushing himself to the limit for a long period of time, which even the most willed person will collapse at some point.
Another aspect is that Luffy will need to accept help from others if he wishes to achieve his dream. Just from this fight alone, we've gotten a clear idea that Luffy would've been fighting an uphill battle if it wasn't for Law. Even then Doflamingo has taken these hits and has still kept getting back up. Luffy is going to face monsters even stronger than Doflamingo in the future. In order to become better, he will need to keep pushing past his limits, but the only possible way to do that is have back-up to allow him to recover after a bit. Much of this arc's success has depended on others helping, whether it's the dwarves allowing access to the factory, or Sabo being there to get Luffy out of a bind. From this arc, we and Luffy can see that his success will depend on having others there for him, as the world is too big for just him and his crew to take on.
People keep saying Doflamingo is hax, and in some cases that may be. However, this is also to show just what's around the corner when it comes to the Yonko fights. If Doflamingo is afraid of Kaido, just what kind of beast is he? With the fight being what it is, we can get an idea of just how far Luffy still has to go if he wants to take on the strongest by himself. Most likely he will be fighting with others against the likes of Big Mom and Kaido.
Maybe when certain events happen later in the series, some of the aspects people don't like now will become a positive. It can be easy to judge certain aspects when we don't have the full picture, and fear that something you don't like can lead to worst case scenario. That's not to say it doesn't happen, but sometimes it's best to wait and see, then make a full judgment.