This poem, in my opinion, is largely just supposed to be playful and funny. But I would argue that it is also meant to critique the society of Macneice's time. This poem was written in the late 1930s.
I would argue that the poem is meant partly to lament the difficulty of getting ahead in life. This is especially evident in the last stanza where he says that no matter what you do you can't keep your profits or "hold up the weather." Please note that "glass" means barometer -- when it is falling that means a storm is coming (the atmospheric pressure is falling).
However, the poem also criticizes all classes of society. It talks about people who want to sit around for 50 years and get a pension. It talks about the middle classes who care about nothing but money and fun (a bit of skirt in a taxi). And I believe he is criticizing the upper classes with their python shoes and hunting trophies. All classes, to him, are shallow -- they don't really want to improve themselves or think -- they just want material things.
So, overall, I think it's a fun poem that is also meant to be a critique of the society of the time.