PostgreSQL extended statistics
I think your best bet would be to set in place a mean to monitor the stats of relevant tables and indexes counters:
https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-ALL-TABLES-VIEW
Specially the:
   seq_scan bigint

   Number of sequential scans initiated on this table

   seq_tup_read bigint

   Number of live rows fetched by sequential scans

   iseq_scan bigint

   Number of sequential scans initiated on this table

   seq_tup_read bigint

   Number of live rows fetched by sequential scans

   idx_scan bigint

   Number of index scans initiated on this table

   idx_tup_fetch bigint

   Number of live rows fetched by index scansdx_scan bigint

   Number of index scans initiated on this table

   idx_tup_fetch bigint

   Number of live rows fetched by index scans

https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-ALL-INDEXES-VIEW
idx_scan bigint

Number of index scans initiated on this index

idx_tup_read bigint

Number of index entries returned by scans on this index

idx_tup_fetch bigint

Number of live table rows fetched by simple index scans using this index