I've long thought that Apple needs a full time COO. When Cook was in that role he managed the supply time as well as anyone could given Steve Jobs' propensity to make last minute changes. But he can't do that and be the CEO at the same time.
That said, some people view the past with rose colored glasses. The original iPhone sold 275,000 its first weekend and there were long lines. The lines for the iPad 2 stretched for blocks at the launch date. It took 3 months for supply of the iPhone 4s to match demand and Apple resorted to an in store reservation system.
It's obvious they had supply chain issues with this, and likely development difficulties since they made the decision to make it smaller than any other similar device out there. I doubt they were able to move the S1 chip to Samsung's 14nm process (which should help battery life in future generations) so they had to use other means to get the battery to last 18 hours. This is a gen 1 product and they experienced gen 1 issues at multiple stages. That said, I'd rather get it late than for Apple to release a half baked product. I'm sure it isn't perfect, but even from the most negative reviews out there this doesn't seem like a half baked product.