Is a 2:2 degree still a achievement?

Depends on the individual. I'm mostly proud of my 2.2 because a lot of people in my situation would have dropped out of uni, let alone finish all 3 years, complete a dissertation and graduate with a lower second class degree. I do get frustrated because of the barriers I face with not getting a 2.1/first, but the area I want to work in is very work experienced-focused which I have plenty of.

Grade inflation

Well if I can’t ever convince you, I won’t bother showing you the evidence that proves grade inflation.

There’s many reasons why that grade inflation exists.

TBH if I got a 2:2 I would not be very happy with myself. I got a 2:1 and still currently looking for work. However some employers require you to have obtained a minimum 2:2 but not all.

The fact is a 2:2, 2:1 or even a 1st does not automatically get you a job which I found out really late. Work experience and skills VERY important.

1sts and 2.1s are far more common than they were twenty years ago.

For possibly many other reasons, not for "grade inflation".

Counter-example:

% of people being awarded a First Class at Cambridge was 13% in 1980, 29.8% in 2000, and 23% in 2010. Looking at the difference in % change between 2010 and 1980 is quite significant, but you're ignoring that the proportion of people achieving a First has actually decreased from 2000.

You shouldn't care if other people think your degree classification is an achievement or not, so long as you know you did your best in your personal situation. The only person you should be trying to impress is yourself.

Some people I know, myself included, went through the hardest times of their lives during their 3 year undergrad degrees so to achieve a degree at all is a big thing for them. I was upset with my grade at first but now, 2 postgraduate medicine interviews later, I realised it all depends what you do with it!

Has it decreased by 16.8%?

You're completely disregarding the different circumstances students were in 20 years ago.
You could argue that a 2.1 wasn't needed to get a job twenty years ago, let alone a First. Only the ones who truly cared about their education and achievements really put the effort in to get a First.

Now, you won't be able to find a graduate scheme without them asking for at least a 2.1. Students are forced to make sure they at least get a 2.1, and because a lot of students get 2.1's, to differentiate themselves from the "average", more and more students aim to get Firsts in their degrees.

Statistics like this completely disregard the different circumstances faced by students in different eras. I'm sure there are many other reasons that has lead to the gradual increase of Firsts being awarded over the last 20 years.

As someone who graduated around 20 years ago I can assure you that you're talking utter crap

And you are one single person, you don't speak for everyone's experience.

https://forums.digitalspy.com/discussion/2041661/has-applying-for-jobs-changed-from-the-70s-80s-90s-to-today

This thread and this article says different. You are completely disregarding the different level of pressure placed on students now.

https://www.theguardian.com/education/2016/jun/24/has-university-life-changed-student-experience-past-present-parents-vox-pops

For possibly many other reasons, not for "grade inflation".

Counter-example:

% of people being awarded a First Class at Cambridge was 13% in 1980, 29.8% in 2000, and 23% in 2010. Looking at the difference in % change between 2010 and 1980 is quite significant, but you're ignoring that the proportion of people achieving a First has actually decreased from 2000.

Let’s be mindful that about 90% of Cambridge grads are coming out with a 2.1 or above too, so it is difficult for it to be “inflated” when it’s already high.

Although it tends to be “easier” to get higher percentages in BScs where their content is more factually correct with more right or wrong answers, compared to arts courses where there is often a percentage cap of 80% or 90% where the subject is open to interpretation/opinion.