Well if you explore what Marx's labour term means and is (Capital's definitions and The German Ideology) you will find out that labour is what is done to keep up society, to reproduce and such. Its form is dependent on the material relations and how labour is done (and it will be more and more alienated) depends on the social relations which spring form that, too.

So work isn't wage work that is aimless, yes, but you can easily work alone and bestow value on something.

The analysis of LTV production within capital that Marx refined from Ricardo and Smith (and in some elements Says) did already reduce the field more and more that Marx is analyzing as introduction for the workers reading his book the system of value creation in capitalist systems in which factories and wage work are common and "working alone" is impossible for the proletarians, since they are doubly free (own no means of production, so they can't produce goods on their own since police violence enforces that - and are free to leave what areas they are born in).

Work that is aimlessly in the sense of not producing - at least societal statistically averaged - is just not work, the problem and question isn't if it bestows value or not, when it isn't work.