Well there is nothing wrong with liking things that are "not as common".

But one thing we need to admit:
If something is common, and it's being purchased in huge numbers buy folks that work hard to get their money, there is probably a reason it's so popular. In the USA the 30-06 and the 308 are more popular then the 270 today and the 308 was in 3rd place in the 60s and 70s, the 270 being #2

I have had very good success with many common guns and calibers. Ones that are or at one time were common still work as well as they ever did. With upgrades is guns and powder, some of the oldest common ones are better today they they were in their golden age.

45 Colt 1873
45-70 1873
303 Brit. 1888
8X57 1888
7X57 1892
6.5X55 1893
30-30 Win 1895
404 Jeffery 1906
9.3X62 1905
30-06 1906
375H&H 1912
270 Win. 1925
and there are many more.

New cartridges come and go. Some come and stay.

But no matter what new goodie comes out, it doesn't mean the old one, which was quite good, suddenly becomes bad.