I'm not sure clothing isn't mostly automated by now. If not, it will be. The larger problem is, Nobody is needed for hand labor any more (or soon that will be the case). What do we do with the uneducated masses then? Educate them? We absolutely don't need a billion more engineers. Then what? I have no answer.
The core of Marxism basically boils down to the problem you set out above. One could summarise the core of Marxism like this:
Capitalism is exceptionally good at improving production, to the point where it will eventually put people out of work, and throw a growing number people back into poverty, and that is when a society is ready for a socialist revolution:
When all basic wants can be met, but no longer are solely for the reason of distribution rather than production.
In The German Ideology (1845), Marx warned that an attempt at a socialist revolution in a society that is not sufficiently advanced was doomed to failure as it would just make want common, and class differences would re-assert themselves. No points for recognising the long string of examples where this actually happened.
Every other part of Marxist theory pretty much serves to underpin or expand on that core.
Unfortunately, garment processing is one field where automation is way, way behind other fields due to fundamental technical problems. There has been little to no progress in the past few decades compared to other related fields, notably fabric production (which is almost entirely automated now).
