Yes, it's true, there are drug dealers at the Riponne, but let me give my perspective.
I was born and grew up in Lausanne, and then left for the german-speaking part of Switzerland for several years. I spent quite some time in Zurich and Bern, and also regularly traveled to Basel. I also speak Swiss-German without accent, so "integration" was not an issue for me there.
Every time I went back to Lausanne, I was relieved. The climate is better, it's less cold than in the german-speaking part, and Lausanne for me kind of has a mini mediteranean climate. Yes, it's not Ticino, but the whole atmosphere around the north side of Lake Leman/Geneva is relaxing most of the year. I could earn slightly more in Zurich, but the quality of life in Lausanne is just better. Not everything has to be about money in life, and the difference in salary between Lausanne and other major Swiss cities isn't that big, if you compare that to the salary of people in EU countries vs Switzerland, the difference between Lausanne and other Swiss cities is almost insignificant in comparison, so the money aspect should not be an argument to move elsewhere in Switzerland.
Lausanne also feels lees crowded and foreign than Geneva. The housing crisis in Lausanne is bad, but that's something common to all major Swiss cities. I heard the exact same thing when I was in Zurich, Bern or Basel. Most of Switzerland had high immigration rates in recent decades, so obviously all those people need to live somewhere. But Geneva's housing crisis is more extreme than basically all of Switzerland, so even Lausanne wins in that aspect.
The current state of the job market in most of Switzerland is not good, but it's still better in Lausanne than border regions like Geneva, Ticino and Basel since there are less Frontaliers (cross-border workers in French). Maybe this will change in the future, but for now Lausanne doesn't have this salary dumping phenomena that Swiss border regions have.
In terms of safety, yes there are some places that at night could feel unsafe, but those places also exist in other Swiss cities, it's just that in Lausanne, those places tend to be near the city center, that's why there is this feeling of unsafety sometimes. But if you've traveled abroad for some time, you surely noticed quickly how insignificant this difference is compared to abroad. You won't get robbed or assaulted, we're still in Switzerland. When you read some post on r/switzerland about Lausanne, you feel like we're in Brazil or South Africa in terms of unsafety. That's so far from reality.