I suggest that you ignore university rankings. If you analyse how the rankings are compiled you may see that they are of little value. Quantitative measurements sometimes masquerade as qualitative measurements, and there is plenty of room for subjectivity.
Graduates of some universities do better than others because those graduates are the most able people in their cohorts, and those people gravitate to universities in the Russell Group and some others, which have the highest entrance criteria.
When seeking a job, you will be judged on your abilities, not simply on the name of your university. But it would be unrealistic to suggest that an employer is likely to regard a candidate who has a 2.1 from the University of Obscure as equivalent to, say, a candidate who has a 2.1 from the LSE. The difference between the two candidates may become evident even if the employer assesses university-blind.
If you are a high achiever, you might feel insufficiently challenged at some universities, where the entrance criteria are lower, because the university has to pitch its teaching at the ability range of its student population.
Cheap is cheap. Pay peanuts, get monkeys is true for many things in life.