Cosmo New Year

Don't we already have Pokemon?

The idea of a fire spitting flying scaled snake like dragon seems as plausible as a sniper-rifle-mace-pistol-sword.

Nature tends to optimize a single task e.g. night hunting for bats, anteaters, and even Canine transmissible venereal tumor.... in a single ecological niche...
I can't imaging in what ecological niche a dragon would fit in... (i won't say it is not possible, as evolution already provided lots of very unusual creatures, but for me it just seems not plausible)

Nature sometimes optimizes brain power such as in case of rats, orcas and humans

We could have wyvern-style dragons that evolved from the Archosauria lineage, but a hexapodal (6-limbed) dragon would be unfortunately impossible given the natural history of this planet - evolution seems to have favored tetrapods, and in my experience, there are no known hexapod vertebrates in the fossil record. To make the hexapodal dragon feasible, you have to establish an entirely new offshoot of vertebrates and work your way up the evolutionary tree from there to make it believable. That's a lot of world-building right there, so it would be easier to assume that dragons were 4-limbed, like pterosaurs were, and work out the evolution of the structures needed for firebreathing - a lot easier than trying to justify a hexapod in a world of tetrapods.