Yes I have that mod and I have increased the time it take to skill up. I play with long life though, so the end result will be the same. I want them to try their best and still only a select few will make it to the top or even above lvl 5-6. Maybe also reduce hourly pay for most of the jobs, especial those in the lower sector. Only thing I can think of to make them stay poor a bit longer is to increase bills to a ridiculous amount. Harder grades for kids and teenagers, (haven't tried uni yet so don't know about that),
With no education and average high school grade, very few are able to climb more than a few steps on their chosen job. If you work at a restaurant, but don't have a chef education, you are not likely to climb higher than a waiter, no matter how many books you read about cooking or how much you cook at home.
So a bit more realist, harder to get a promotion, possibly a max lvl for different final grades for teens, (unless they go to uni), and lower wages for the lower paying jobs.
Another idea that I can't remember if I downloaded in Sims 2 or 3, is a bush that act like a loan. Every bush you buy will give you 1000 or 5000 simelons or such, but you have to pay 10% interest, not sure if it was pr day or pr bill, (2 times pr week). Would be a realist way to play on how many people spend more than their means and end up in a situation where they end up taking more loans to pay their old once in a vicious circle. Starting them out with no money except for the lot and have to buy those bushes to get the most basic, will also make for a hard start.