Is the macbook 2015 still usable to this day?
It's a sad reflection of these forums that you would have this impression and feel the need to ask.
For your stated usage, it's a fine laptop.
It's obviously no powerhouse, but for general purpose tasks, it performs well. I'm quite sensitive to computer performance, and so I know what others are referring to, but their perspective is generally not in line with the other 92% of computer users out in the "real world". OTOH, if you're someone who notices 1/10th second performance differences, and benchmarking UI animations, then its probably not the laptop for you.
Its best feature is its size and weight along with an excellent screen -
physically it's closer to an iPad than a more traditional 13" laptop for me. If those aren't very important, then consider a MacBook Air.
I've compared 2015 keyboard to the 2017 keyboard side by side. In my "testing", the 2017 keyboard is a slightly noticeable improvement in feel and sound, but most people wouldn't be able to tell the difference without such a side by side comparison or without extensive prior experience. One of the first things I did when I got mine, was try one of those online typing tests - I was faster on the MB keyboard than any previous test I'd done. It takes a few days to get used, and the keys are slightly more "clacky" sounding, but again, it's a non-issue for 90% of users.
All current Mac laptops have a similar keyboard design, and they
are more "fragile" than previous keyboards, but it's been blown hysterically out of proportion. It wouldn't stop me from buying one or recommending one. Just don't eat over the keyboard (and I'd give the same advice for ANY computer ).
If a few hundred bucks isn't a big deal, I'd definitely recommend a new(er) one, but if the price is right and you have very limited budget, a 2015 MB (any CPU) should serve you well.
Best of luck!