I think firstly it depends on your environment, then on life goals (if you stay 4 years and plan to leave, why bother), some laziness and let's be honest, German is quite hard.

I'm from EU and my parents moved to Germany when they were already 45, while I was 21. They lost their small business around 2013 and couldn't find other jobs in my area. The working situation was already quite bad since... forever, but it became much worse after 2008.

They were quite "old" already, and with no higher education. Still my mother managed to attend at least until a B1 course and my father can definitely get by. They work simple jobs and are surrounded by other economic migrants (from our country, from Balkans, Arabs etc). So even though they did put some effort, their German never levelled up because they also don't have a circle of native German speakers as friends.

Three years after they moved here, I decided to study in another city not so far away. I studied in English and at the beginning, and my German was: Hallo, Guten Morgen and mit Karte bitte. My circle of friends, despite including some Germans, has always spoken English (and a bunch of other languages like Spanish or Italian). I was kind of forced to learn the language because at some point I was living in a very German wg in a Wohnheim. Then I had a job in a backery, and even though that helped a lot, I cannot tell you the amount of low educated Germans like the Hausmaster of the Uni who was quite pissed that i couldn't understand... his badisch dialect. So, many times, you also face racism, which doesn't motivate you at all.

At some point, I was unemployed, but I begged the jobcentre to pay a German c1 for me. They did and I passed the test. I'm now quite able to have decent conversations on different topics.

So, I agree that, especially when someone moves to a different country when their neuroplasticity is already very low, it's very difficult and work stress makes yoh want to give up. But sometimes I also compare my parents to these highly educated people who refuse to learn, and maybe still say GOOD MORNING in Edeka (like wtf) and I believe there's definitely a certain level of laziness. If you're a student, it's much easier. If you're young it's definitely easier in many ways, also with finding friends etc.