Massive Analytics imports are possible with WP-CLI commands from the console, but there are still some limits even with them. Specifically, it looks like Google limits to 1 million rows the amount of results one can obtain in one request. If your site has a lot of pages, and it is likely that the number of URLs for which Analytics has logged visits for the time range you requested exceeds 1 million, then the dataset Post Pay Counter will import is likely to be incomplete. You can tell if this is the case if the number of pending rows after the request is exactly 1 million (what are the odds that the site had exactly 1 million rows? No more than one in a million).

To circumvent this, one can run multiple requests for shorter timeranges and let the plugin merge the data all together. The following bash script will for example import data from 2018-01-01 to 2021-12-31.

sudo -u www-data wp ppc ga clear
for year in {2018..2021}
do
  for month in {1..12}
  do
    lastday=$(date -d "$month/1 + 1 month - 1 day" "+%d") #https://stackoverflow.com/questions/12381501/how-to-use-bash-to-get-the-last-day-of-each-month-for-the-current-year-without-u
    sudo -u www-data wp ppc ga import --time-start="$year-$month-01" --time-end="$year-$month-$lastday"
    sudo -u www-data wp ppc ga process
  done
done