I'd be amazed if they gave you a refund.
It's hard to build more than one or two types of units in the first five minutes of the game since players wouldn't have been able to research the other units. Maybe you just need to learn how to deal with the early game rush? I think you should watch the replays and ask yourself what you could have done differently to prepare for it or to counter it. Why not just copy your assailant's technique and use it on your next opponent if it is overpowered and unstoppable?
If you think MP is about building all of one unit, then perhaps you're doing something wrong or don't understand how to counter all of that one unit. Sometimes it makes strategic sense to build all of one unit depending on what your opponent is doing. Also, the strategy of this game is about much more than what units you build. Now, each race has three primary fighting units that do damage to enemy ships--Light Frigates, Long Range Frigates, and Heavy Cruisers. These are the ships that kill other ships; the support ships aren't nearly as good at it. So, naturally, you can expect to see a lot of them. The other units are pretty much support units to protect or assist the fighting ships, though I guess someone might also pump out a lot of carriers for bomber spam.
What do you regard as "the most of one thing"? If I build a fleet consisting of 1 Progenitor Mothership, 1 Halcyon Carrier (capital ship), 40 Illuminators, 6 Defense Vessels (anti-strikecraft), 4 Guardians, and two carriers (6 fighters) is that the same as spamming out "one thing"? Most of the ships in that fleet are Illuminators, but there are other important ships, too.
Anyway, please hang in there. It's hard to get up to speed with this game because there are a lot of skilled, experienced pros around, especially on Diplomacy. Have you considered just playing the original Sins for a while? I think you will find that there are more newer players there. Actually, we probably have a higher percentage of newer players around than I have seen in a long time.
Sins really is a great game for online multiplayer once you have learned to hold your own and understand the strategy of the game. I have enjoyed numerous, intense games on Sins, including a great many competitive 5v5, 4v4, and 3v3 games.
