I can't link to specific query results from the American Time Use Survey, but from this page [1], you can check "Avg hrs per day - Socializing and communicating", click "Retrieve Data", then adjust the time range using the dropdowns at the top, to be up to 2003 - 2024. In absolute terms (hours, not percent) there are declines both for the whole period, and from from 2003-2019 (i.e. before the pandemic).

And you can look at the series for "Avg hrs per day for participants - Working at home" and confirm that as expected it is relatively stable through 2019 and jumps in 2020, so the decrease in socializing through 2019 is not about WFH.

[1] https://data.bls.gov/toppicks?survey=tu