Pretty good list. Some comments here mention this is obvious or dated, but I think that in the wild a lot of devs aren't doing these things.
I think there are still a lot of back-end devs which this very much applies to. If you are a back-end dev who has been able to get away with not knowing CSS (and possibly even JS) well, then you need to fix that deficiency. For example, I typically work with a team of developers where I rarely have to touch CSS issues, but on my own projects, I get a lot of enjoyment on this, maybe because it's just a change.
Client side MVC is overkill in a lot of cases, but when doing client work you will come across these, so this is a good suggestion.
Optimization is something that can get left out if you have a dev team in which nobody picks up that piece. For me, I don't do things the client hasn't authorized payment for me to do and I'm generally busy enough that I hit those paid items and then I'm immediately switching to another project. Often my client is another developer who has pieced together a team. Nobody gets paid to do the optimization, maybe because the main developer is sloppy, lazy, or just doesn't know. It's just one of many details which should be covered but is often left out because of deadlines or a tight budget.
I would suggest that you should start applying MVC practises as soon as you start adding Javascript to your page. You don't necessarily need a complex framework, so long as you stick to the separation of concerns.
I think that's something that's best described by "you know it when you run into it" perhaps at the time when stuff starts getting away from you.
I have never used these for client work. My concern was that a client might insist on using these despite your preferences. So, as a freelancer you should be familiar with them because they can have a bit of a learning curve.
It's not like you have to actually do something to minify, unless you are still doing it manually. It should be part of your default stack, any decent framework can do that.
I think there are still a lot of back-end devs which this very much applies to. If you are a back-end dev who has been able to get away with not knowing CSS (and possibly even JS) well, then you need to fix that deficiency. For example, I typically work with a team of developers where I rarely have to touch CSS issues, but on my own projects, I get a lot of enjoyment on this, maybe because it's just a change.
Client side MVC is overkill in a lot of cases, but when doing client work you will come across these, so this is a good suggestion.
Optimization is something that can get left out if you have a dev team in which nobody picks up that piece. For me, I don't do things the client hasn't authorized payment for me to do and I'm generally busy enough that I hit those paid items and then I'm immediately switching to another project. Often my client is another developer who has pieced together a team. Nobody gets paid to do the optimization, maybe because the main developer is sloppy, lazy, or just doesn't know. It's just one of many details which should be covered but is often left out because of deadlines or a tight budget.