"I’ve seen various comments from people on social media saying they lost all their pension and it was worth next to nothing etc."
Without knowing a lot more it's hard to know what has happened to these people. These could be covering a variety of different (mostly historical issues); poor investment returns, unrealistic projections (so people expected to get much better returns than they did), people who have only saved very small amounts and been surprised it isn't worth much, low annuity rates (these have plummeted), old style schemes which failed...
Many older pensions had guaranteed benefits - so the investor put in money with some guarantee of what they would get back, often in the form of a guaranteed annuity rate they would be offered at retirement. As the financial environment changed these guarantees became incredibly expensive for the companies to fund - and in the case of Equitable (often the source of these stories) the company couldn't keep paying and people lost money. There were also other types of complex product, things like with-profits, some of which were badly sold and badly managed..
This happened over 20 years ago, and pension/insurer/financial services regulation is massively different now. It's much more stringent, and companies don't offer as many guarantees now because wherever they have committeed to a specific future payment to a client they have to show that they will be able to meet that payment even under pretty dire circumstances. I'm simplifying (I work in this area!) but it is hugely more strict than it was.
The sort of pension you are looking at doesn't have these sort of issues anyway - it's a defined contribution scheme so there is no guaranteed return. What you get at the end depends on how your investments perform; it's actually a pretty simple product by comparison to some of the older ones.
There is always a risk associated with investment performance; your fund will be in shares, bonds etc and their value goes up and down so some years will be great and others not so good but over the length of time you are saving those bumps should average out and your money should grow in real terms over the time you are saving. If you put your money in a bank account or a cash ISA you won't ever see its value decline in monetary terms, but the returns will be so poor just now that the value will decline in real terms. The best buy cash ISA just now is paying about 1.5%, but inflation is running at 3% so your money will grow at a lower rate than your costs. Imagine the impact of that over 30 years...
I hope that makes sense - please feel free to ask if it doesn't!