It's an HDD.
Add in: various security measures, such as memory randomization and checking apps signed correctly or in the allow list, takes some amount of effort.
Also, how much stuff is firing off at start as part of Login Items and or other background apps.
If have an SSD in my old Mac, and one thing that seems to grind the boot to a halt is cloud services, and mostly Dropbox: that one seems to drag down the system as it updates things. iTunes too.
It's a common complaint on this board. Common answer seems to be "get an SSD" as it seems like OS and apps are more geared to people having SSDs in their devices these days.