High Peak Liberal DemocratsLib Dem members were the most likely to say they delivered leaflets, and the only party to have seen an increase on that measure since 2015:

Overall, levels of claimed campaigning was down on 2015, due (I suspect) to the snap nature of the election campaign. So you shouldn't read to much into the decline in the Labour figure; that isn't necessarily a verdict on new versus old Labour members.
As for the importance of this figure: leaflet delivery works (see the links here, featuring a cute dog*).
Data from "Twice in a row? UK party members' campaign activity in the 2015 and 2017 general elections compared" by Tim Bale, Paul Webb and Monica Poletti.
* Yes, I'll do anything to up your dwell time on this site.
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