Forget skills: that's difficult to estimate, because (almost by definition) you don't remember what you have forgotten. When you try to review the rests of your ancient skills, the result is "I remember all this, and this, and this...". It needs an external input to realize that you have forgotten all that, and that, an that too. When I threw away my notes just 10 years after the diplomas, there were complete courses I didn't remember to have attended. OK, not in the domains that interested me.
The other aspect is that one refreshes quickly what was already known. Having forgotten isn't the same as having never known.
When applying for jobs, keep in mind that the employer rarely tells the true reason for not hiring you. Most often, the recruiter preferred someone else, but won't tell you because this decision is subjective and hard to justify, so he seeks simple explanations. In a different opportunity where he would not prefer a competitor, he wouldn't tell "too long out of job". And then, there are the truly embarrassing reasons, like "don't want a Latino / a Muslim / a woman / etc" which would be illegal in many countries. Or even more often, the company has published a job description but cancelled the position because it lacks money or plans to sell the subsidiary - something they won't tell the customers, creditors, competitors. In such situation, women think "because I'm a women", black people "because I'm black", older people "because I'm older" and so on.
Most times, a personal director considers his duty to make reproaches to you, as a part of the present and future negotiations for money.
You get easily paranoid for searching for a job, but you shouldn't.