Those are all advantages, but MC's unofficial mod support is very good, and has much of that.
The real problem isn't MT's hypothetical mod support, it's that people aren't building the kind of mods that you get in MC: There's no BC, IC2, AE, TC5, TE4, CC, Ars Magica, Blood Magic, TConstruct, Forestry, FMP, RC, EE3, and so on. Those mods are a big part of why MC is what it so great, and MT can't get away with just copying them: It can copy, sure, but it should also have its own mods, and they should be good ones, because otherwise there's no reason to play it over MC.
It doesn't matter how good your mod support is. It matters how good your modding scene is. And MC has one of the best since HL.
The real problem isn't MT's hypothetical mod support, it's that people aren't building the kind of mods that you get in MC: There's no BC, IC2, AE, TC5, TE4, CC, Ars Magica, Blood Magic, TConstruct, Forestry, FMP, RC, EE3, and so on. Those mods are a big part of why MC is what it so great, and MT can't get away with just copying them: It can copy, sure, but it should also have its own mods, and they should be good ones, because otherwise there's no reason to play it over MC.
It doesn't matter how good your mod support is. It matters how good your modding scene is. And MC has one of the best since HL.