You must remove Avast before doing anything else. We see reports here with slow hard drive flags that proved to to aggravated by useless third-party anti-virus. Once you remove that, a new EtreCheck run will give a clearer picture.
However, based on my experience and reports posted here, your hard drive is simply too slow, failing or not. I have the very same MacBook Pro model and it was sloooow. These are data on app launch times as I added hardware upgrades. When I started, its original hard drive showed as "healthy." So, step by step:
App launch time data from one of my upgraded MacBookPro9,2:
🔹Base system as shipped:
4GB RAM and slow SATA 3GBps 5400rpm hard drive: Office and Photoshop Elements took 15-18 seconds to be ready to use.
🔹First upgrade, doubling the RAM:
8GB RAM and slow SATA 3GBps 5400rpm hard drive: Office and Photoshop Elements took 15-18 seconds to be ready to use.
🔹Second upgrade, inexpensive solid-state drive
8GB RAM and fast SATA 6GBps SSD: Office and Photoshop Elements take under 4 seconds to be ready to use.
So adding RAM will not speed up app launch or boot times noticeably. However, and even considering your computer was not stressed for RAM at the time of the test, RAM is cheap and you should do at least 8GB. If nothing else, do it for the peace of mind you get knowing you have enough RAM. It also gets removed from the suspect list that way. My 2102 MBP has never shown needing more that 8GB RAM for the use it gets—MS Word; Excel: Photoshop Elements; browsing and mail.
Chances of your problems being a slow factory drive are about 99 percent if the condition persists after you evict Avast. Here are more data directly from EtreCheck repots comparing your MacBook Pro 9,2 with its slow spinny hard drive to my MacBook Pro 9,2 with a cheap solid state drive.
Your drive performance:
Performance:
System Load: 1.28 (1 min ago) 1.35 (5 min ago) 1.32 (15 min ago)
Nominal I/O speed: 3.18 MB/s
File system: 86.72 seconds
Write speed: 39 MB/s
Read speed: 48 MB/s
My drive performance:
Performance:
System Load: 1.61 (1 min ago) 1.60 (5 min ago) 2.94 (15 min ago)
Nominal I/O speed: 0.15 MB/s
File system: 28.20 seconds
Write speed: 487 MB/s
Read speed: 482 MB/s
Same computer. Ten times faster data transfer. That upgrade including a new drive cable (highly recommended) cost about US $120 for parts and I did mine at home in about 30 minutes. Before the SSD i did not look forward to using my MBP before; now I love using it.
Yes, it is an 8-year old computer. However, if everything else is working properly and you don't want an expensive new MBP that is as fragile as an eggshell, you may find it worth upgrading a bit. It is running the latest OS version, you can get "under the hood" to change its bits, and it has an optical drive. Your call, but I plan to wring all the service out of mine that I can before have to get something new.