I'm a bit of a curmudgeon when it comes to stamp collecting, and only like the pre-WW2 ones when stamps were lovingly engraved.
After the war post offices realized they could sell stamps to collectors who wanted "uncancelled" stamps, meaning they were pure profit for the P.O. Stamps were sold from the P.O. directly to collectors who never used them for postage. Hence, the variety of stamps exploded, and the designs were cheaply done. In my not so humble opinion, they wrecked the hobby with this, and it shows in that stamps printed after WW2 have little to no collector value.
The same thing happened to coin collecting. For example, a US mint collector set from the 1970s is worth its metal value today. They look nice, but that's it.
After the war post offices realized they could sell stamps to collectors who wanted "uncancelled" stamps, meaning they were pure profit for the P.O. Stamps were sold from the P.O. directly to collectors who never used them for postage. Hence, the variety of stamps exploded, and the designs were cheaply done. In my not so humble opinion, they wrecked the hobby with this, and it shows in that stamps printed after WW2 have little to no collector value.
The same thing happened to coin collecting. For example, a US mint collector set from the 1970s is worth its metal value today. They look nice, but that's it.