Bitcoin got first mover advantage. I don't think its popularity is due to it getting the incentive mix "just right".
Besides, the characteristics of a "good coin" depend entirely on who you are and what your goals are. Some people want to gamble and get rich, others are looking for a reliable store of value, others are looking to transact. The ideal coin will have different properties for each of these people, but no coin will be able to satisfy all three groups completely. They all need one another and they all have competing goals.
Fair point. I don't think that Bitcoin's parameters are necessarily "just right", but I'd argue that they are "close enough". An ideal coin that, as you state yourself, does not exist, but neither does an ideal traditional currency. Every currency and payment system out there has it's flaws, but not every flaw is necessarily fatal.
Particularly the deflation argument does not predict that Bitcoin will fail, it states that if Bitcoin replaces traditional currency, the economy will fail. If you choose to believe it however, it's an argument to hoard Bitcoin from a rational economic perspective.
People looking to criticize Bitcoin should rather focus on the centralized mining problem.
Besides, the characteristics of a "good coin" depend entirely on who you are and what your goals are. Some people want to gamble and get rich, others are looking for a reliable store of value, others are looking to transact. The ideal coin will have different properties for each of these people, but no coin will be able to satisfy all three groups completely. They all need one another and they all have competing goals.