I think in the days of internet and potentially mostly phone/zoom doctors' appointments it probably is quite easy up to a point.
It can be hard to tell where deliberate deception starts and psychological influence ends though.
So one of my dc quite likes a bit of sympathy. She has self-diagnosed a few times on various things. It normally goes along the lines of she google-searches for a symptom and comes up with something extreme (because let's be fair, no one blogs "I had this ordinary symptom that leads in 99.9% of cases to nothing"; they're all "I'm in the 0.001% of people for whom this symptom meant something devastating).
Once she has found the condition she thinks she might have, she starts looking at the other symptoms, and she'll often "realise" that actually she has most of them - having not thought about them until that point.
She is not lying. She is not making it up. But her brain is panicking and producing the symptoms to order. Once I manage to prove to her (almost always) that she definitely doesn't have whatever it is often all the symptoms clear, including the initial one.
Think about it. If someone says to you that eg they smell gas, you probably start sniffing. There's that funny smell in the corner. Is that gas? I'm sure it smells like gas...
I once thought I had MS due to having odd pupil sizes. Not sure why I linked onto that, but I spent two weeks after I'd decided that, with constant pins and needles in my limbs, odd numb patches and feeling dizzy, which were all symptoms in the article I'd read that connected odd pupil sizes with MS. Eventually I went to the doctor who, bless him, ran a couple of tests, and told me he couldn't guarantee that I never would get MS but he was confident that I didn't currently have it. Days later, I was getting ready for bed and realised that I had had none of the extra symptoms since I'd walked out of the doctor's surgery.
I still have odd pupil sizes, especially first thing in the morning, but haven't had those symptoms in the now 30 years since. Power of the mind.
There was a funny book written in I think the 30s (Doctor about the House?) where he reads the medical dictionary and concludes he has everything in it except Housemaid's Knee, so the internet isn't all to blame.
And there are a number of conditions for which it is a case of connecting symptoms and ruling out anything else. So if someone wants to find something wrong, then they can use the internet to find the symptoms and tell the doctor they have those symptoms.
No doctor is going to say that they haven't got the symptoms that they say they have, although my GP did once disprove one of dd's by waving a chocolate bar in front of her and point out she couldn't have jumped that high with whatever (appendicitis, I think) she thought she had.
But, to me, the fact that these conditions are easily faked makes it doubly bad in my eyes to fake it. Because the people who genuinely have the conditions then end up being doubted by others, and people faking it makes people doubt so much more.