The hard drive looks healthy although attribute# 220 "Disk Shift" is non-zero which may indicate a problem. This is not one of the attributes I normally monitor since I'm not sure how drive manufacturers handle this attribute. The "Load Cycle Count" is at 64% which is "Ok" for now, but as this value decreases it means the head is becoming worn where the drive can slow down or misbehave (especially once it is at 1%). In my experience the hard drives in laptops don't usually last more than 3K to 5K power on hours and your drive is at 4,100 hours since they get jostled so much (G-Sense error rate is 12K, and Free Fall Sensor is 1,400 which definitely decreases the health of the drive even if everything is Ok). Also some performance issues will not show up in the drive's health report.
Upgrading to an SSD would improve system performance since the Apple hard drives are really slow even when they are working well. A Crucial MX500 series SSD is a good compromise on price and performance (stay away from the Crucial BX500 series since it can be as slow as a hard drive and it tends to overheat). Keep in mind many SSDs today are just low end budget economy models that can run as slow as a hard drive. It is very difficult find a mid to high end SSD these days.
You can try running Disk Utility First Aid on the hidden Container to make sure the file system is Ok. Within Disk Utility you may need to click "View" and select "Show All Devices" so that the hidden Container appears on the left pane of Disk Utility. Even if First Aid says everything is "Ok" click "Show Details" and manually scroll back through the report to see if there are any unfixed errors listed. If there are any unfixed errors listed, then see whether First Aid can fix them while booted into Recovery Mode, otherwise you will need to erase the whole physical drive before restoring from a backup or clone.
The only software shown in your EtreCheck report that I would be concerned about is the "ExamSoft" software. You may want to uninstall this software by following the developer's instructions.
I also see you have a memory upgrade on this laptop. What is the make & model of the 4GB memory module and how long has it been installed?
It never hurts to run the Apple Diagnostics to see if any hardware issues are detected.
No matter what upgrading to an SSD is the best thing to do to improve system performance of an older computer.
