To chime in on how English law approaches this (and perhaps amplify some of the good points already made): the common law position is that any restraint of trade is contrary to public policy and so should not be enforced unless some exception can be shown.
Post employment restrictions fall under the doctrine of restraint of trade - which explains why we use "gardening leave". While you are employed you and your employer have a relationship which includes a duty of loyalty by you to your employer. They have duties such as a duty to pay you for your work. By default they should also be offering you work, so a specific "gardening leave" clause is required to keep you at home, bound by restrictive covenants but without work and being paid.
After employment, it is much harder to make restrictions that will bite. Typically an employer must show there is some legitimate interest they are protecting and that it is reasonable to do so.
Hence: non-solicitation of clients tends to be easier to justify, though only if an employee actually had some kind of relationship with or knowledge of those clients. Whereas a non-compete is much harder to justify. It is also harder to make reasonable, hence time/space/sectoral limitations.
Looking at confidentiality: the default established in the amusingly named Faccenda Chicken v Fowler (Mr Fowler was a frozen chicken sales lead). It is that you are bound by the usual duties of confidentiality that arise when anyone has confidential information but that you cannot be prevented from using information gained while working that is part of your normal skill acquired as part of the job unless that is so secret as to amount to a "trade secret".
In this case, Mr Fowler knew where to sell chicken (from having done so). While this was confidential, he was able to use that information (not being a trade secret) in setting up a competing frozen chicken sale network.
The core idea is that you can't stop someone plying their normal trade.
That's the default. Obviously if you sign an agreement that imposes post-contract confidentiality obligations it can go further than Faccenda Chicken, but if it went too far, it would also be vulnerable to the rule against restraint of trade.
In short:this sort of "you cannot work in the industry" idea is very unlikely to work in England and Wales (and I suspect the rest of the UK - though I am strictly only an English lawyer).
That said: there is still value in reading your contract of employment carefully and making sure that you are happy with it.