As Bitcoin falls further behind on the mempool queue, many entries expire after a set time (default of 14 days) but many remain and as Bitcoin regresses through the queue, the cumulative ages cause the average age to skyrocket.  

Bitcoin transaction confirmation time:

1st graph is June, 2023 with a new high of 25 hours.
2nd graph is July, 2023 with a new high of 77 hours.
3rd graph is Sept, 2023 with a new high of 181 hours.