Well this is depressing, but the article has a point. The career prospects of the job are incredibly limited. I'm sure all language teachers have met weird people who somehow manage to function in the role, despite minor mental health issues or substance abuse problems. Language schools and in company training firms are exploitative as fuck and basically pay a fraction of what the client is paying them for doing pretty much fuck all aside the marketing and administrative side of things.
Plenty of the teachers I've met in TEFL are pretty thick with very little language awareness. Of course, it's natural for new teachers to be a bit ignorant of many of the linguistic features of their native language that might confuse non-natives, but the ones who don't ever address this are either incredibly lazy, thinking they can just phone it in every lesson by virtue of being a native speaker, or too thick to master the abstract thinking necessary to understand the language in the concrete fashion that might help a struggling student.
I lucked out a bit and found a position at a quasi-respectable institution (not a language school or in-company training firm). Had I not, I doubt I'd still be in this line of work and probably would've already gone back to university or at least taken a crappy full-time job. There's only so long someone can run around a city teaching apathetic people in offices who clearly have limited English simply because they don't want to integrate English into their daily life in any sense or form and think by sitting in a class for 1.5 hours a week they're entitled to sudden improvement in their capacities. That said, we're still basically wage slaves with no job security: contracts are signed on a per course basis, you have no way of knowing your income in six months time, and there's very little continuity to the learning process. The only difference is that you're treated with a bit more respect by the students/staff and you get more money per hour.
I hope I'm gaining useful skills in some sense or form. The challenge of teaching young students (18 - 25) is enjoyable and avoids that hassle of dealing with cynical middle age types (at this point I feel that in most cases if they were going to become proficient they would've already) or children (too many complications). It's also great to have the opportunity to gain language skills. Although, constantly working with English is definitely not the most direct route to that.
Personally, I'm looking at furthering my education to allow me to switch to teaching something I find more interesting. I'm sick of being a 2nd class teacher working around people people paid 1000 euros for 12 hours work a week.
Of the language teachers I've met, many seem to fall into similar categories: you've got your rich older types who burned out of what they were doing before, but have enough money saved to be set for life and are just doing it because they see it as a low stress job that can earn them money on the side before they claim their fat pension, you've got those who are younger but surprisingly well off who are just doing this a job safe in the knowledge that when their parents die they'll get their hands on a fortune, you've got your housewives who wanted to go back to work now that the kids are a bit older and are just really supplementing their partner's income, you've got the younger 20 something who just want to live abroad and need an income, and finally you've got the older 20 somethings and early 30 somethings who just haven't quite found their way in life yet. Sadly I'm amongst the latter.