I think there are a lot of misconceptions in this thread, so let me just explain what happens:
1. In a single or multiplayer game, capturing an ARS does not unlock any techs. It does open a new ship class for research, of course, but that's the same as in single and in multiplayer. You get the Mark I for free, then have to unlock II and III/IV, as normal.
2. In multiplayer, the entire team gets the new ship class -- the same new ship class. This has always been the case, and so far as I know has had no issues with it; I suspect that in the game a few weeks ago, the player just didn't notice he had a new ship class or something. It wouldn't necessarily have been on the far right of his list, ships have an implicit order to them, so that might have thrown him off if he was looking to the far right only.
3. There are always exactly five ARSes in a game, any game, regardless of the number of players. In an 8-player game, making those limited by player would simply make it so that most of the players would never get any new ship classes, or only one at best. With the implemented approach, everybody gets the same five as these are unlocked. This is part of good co-op design, and not something I'm going to change for something so core; there is no reason to encourage players to be at each other's throats for such a finite and critical resource as ARSes.
4. Of course, in terms of golems and other capturables, those are more limited and don't get shared amongst the whole team. But, the way those are structured is for encouraging player specialization: player A has a golem, player B has mark IV ships, player C has experimental starships, etc. There are enough capturables that everyone can get something interesting, even in an 8-player game, but everybody doesn't get the same thing.
5. In terms of why everybody gets the same thing in the case of the ARS, this is for two reasons. First, given that the received ship is essentially random, it makes it so that nobody on the team is getting luckier than others in terms of what is unlocked. Second, it helps to keep the originally-chosen ships mutually-exclusive. If you unlock microfighters at the start of a game, and I unlock parasites, then those are our specialties and you will never have parasites and I will never have microfighters in that game. The unlocked techs from ARSes pull from the pool of classes that no one on the player team already has (and with 5 bonus ship classes, there are not nearly enough for each player to have 6 total unique classes, even in 4-player, let alone 8-player). Also, keeping the total number of ship classes somewhat limited per game keeps the strong/weak displays shorter, and the planetary summaries less crazy, and less to focus on in that overall game.
In general, this system is not built around making the game easy or a learning experience in co-op, but rather for making it playable at all -- and for not turning this into secretly a competitive game inside a co-op game, which is poor co-op design and all too common. Bear in mind that most of my own play with the game is in 4-player co-op, so it's not a theoretical balance based on what I extrapolate from solo play. In most senses, I think solo play is easier in AI War, and these sorts of things in co-op are what help to make it actually possible to win on 80-planet maps against diff 7 or greater AIs. The amount of territory controlled per player is so much less in co-op that that puts some constraints on players that are not typically there in solo (though, there are greater resources per planet).
I'm not saying that the current system is perfect by any stretch, but it's far from broken and it's definitely not a case of training wheels. The difficulty of the game, especially in co-op, has been creeping up pretty steadily over time with improvements to the AI and changes to the game in general, and if anything I've had to make some concessions recently to make it less brutal at standard difficulty levels.