There is a problem of a false separation between theory and practice here, which I don't think you address sufficiently in your post. For example, with the anarcho-syndicalists and the class struggle: some of their groups and comrades do some very solid work at the workplace but they also tend to be very ambiguous about the trade unions: often their members, while nominally in favour of new 'revolutionary unions', recruit people for the existing unions and serve as lower level union reps, which causes a great deal of confusion. Left communists are trying to be consistent between their theory of unions and their actual practice, which means that most of them reject taking positions as shop stewards (which offers all kinds of opportunities for 'doing' stuff). But I don't think this means that their workplace practice is abstract. On the contrary: they can be involved in strikes and protests and fight for workers' autonomy to be put into practice through assemblies, militant workers' groups and so on. The two main left communist groups can point to many examples where their members have been directly involved in such activities. However, we are not defined simply by our place at work (or study) but as communists take part in much wider intervention, whether in the general struggles of the class, social movements like the ones we saw last year (where I would say many left communists also played a very concrete role where they could) or on issues like war, political and economic crisis, etc.