When playing A game with many players the AI trades techs like crazy with each other. Then it continues down the tech tree of the weapon type that it recieves first. Since they trade like crazy ,most if not all AI races will have the same weapon types and the same defenses against said weapon type. Once this is realized by the human player . Victory is inevitable . simply research the one type noone else uses . and research heavily the defense against the most common type of weapon and you can beat fleets with one or 2 ships If they are equipped properly.
One solution is disable tech trading altogether . but alot of the time the AI races seem to still go down the same lines of research. I propose each race having some kind of random dice roll or something making them choose a "Preferred " weapon type at game start and continue down that line as their primary weapon and then do the same for a secondary weapon type . Their choice of defense Is just as important and should be handled in the same way. to avoid "cookie cutter Weapon/defense specializations. Otherwise the only way to even have a challenge is to disable tech trading altogher.
At least this way every race will differ in their ship types . And I would be forced to make tough decisions . As it stands right now All i have to do is see what the galactic weapon type is and build my ships to counter that. and viola I win regardless of my military size