How could you explain in a short sentence why endpoint protection is important for a computer (laptop in my case).
Not at all. Do not you need.
Just use the Defender and it is good.
Private yes, for a company no ^^
Not enough Internet Security from Kaspersky e.g.
The internet is a minefield. Being unprotected on the road is like unprotected sexual intercourse (number of partners = number of pages visited and services used).
If you don't pay money for something (you pay with your details, but that's another topic), you don't have to expect miracles. But if you pay for some money, then you can also expect to get a working product including update supply.
Furthermore: no backup, no pity.
What you do with it now is your business.