Initially I thought that the OP was just trolling, but I think that he actually has a pretty valid point if I am understanding him correctly.
Years ago almost all work was hourly rate stuff and the average was probably NTD500-550 an hour - so a bit less per hour than today. The difference was that you could easily get 30 to 40 hours a week and earn big bucks at one school and without the need to teach kindy in the mornings. Thereby earning the OP’s suggested NTD70,000-80,000 per month. With pay raises over time it was easy to be earning NTD80,000-100,000 a month if you were willing to put in the hours. The downside of course is that this was all class teaching hours - not admin work - and that can be pretty tough on the old voice box.
Nowadays, even though the average hourly pay is up to around NTD600-650 an hour (not much of an increase over the years) the number of hours that most schools are actually able to offer seems to be much lower than before. It is likely that most teachers start off with about 16 or 18 teaching hours a week these days, which if you only have one employer means that you are only earning a fraction of what you could have earned in years past. There is often no opportunity to take on extra hours at your primary school to earn more money as in many cases these extra hours are just not available. This forces many to either find a second legal employer, or in most cases teach illegally by taking on kindy work or privates to supplement the income.
The above is possibly one of the reasons that monthly salaried positions are indeed the preferred option for new arrivals. Sure they tie you up at the one school all day, but they do guarantee you a monthly income of NTD50,000-65,000 plus some benefits. Average out the pay per time spent at the school and it is not much, but look at your bank balance each month and at least you get the security of knowing that you have money.
OP, yes it is tougher now for newbies in Taiwan to find work and to find good jobs. But as others have pointed out, there are good jobs available but you need to spend time finding these. Also, I think it likely that these types of schools would prefer teachers with teaching experience in Taiwan.
The teaching environment in Taiwan these days is much different to what it was years ago. There is a lot more competition among schools for students. And there is a lot more competition among foreign teachers for jobs. I wouldn’t say that it is an employers market, but foreign teacher these days really need to prove their worth if they want to get the preferred jobs.