I have the base model with 2.5GHz CPU, upgraded to 16GB RAM and an SSD. It's still a completely capable laptop, I really don't feel it has any limitations for average use. It's absolutely powerful enough and can handle anything, except for heavy 4k video editing. I ran large simulations in R, worked on extremely large Excel files, 100s of browser tabs can be open if you want, it really won't struggle. Performance-wise it's really still perfectly fine for most.
My 2 issues are the low res screen and weight. The lack of Retina display is the biggest issue, the screen is just way better on the newer MBPs. Of course the display is not THAT bad but it is significantly worse than Retina displays, which is good enough reason to upgrade to a newer model in my opinion, especially if you spend a lot of time staring at your laptop everyday. It is also a very heavy laptop compared to what's out these days so if you will be taking it around daily with you to work it's not the best option for that.
Given that Apple still sold this laptop in 2016, you can definitely get a few more years out of it.