In such a case I have to watch it to decide if it feels like a western or not.
Some films do this for me, even if they are far away geographically or temporally.
I just stumbled over a book called The 50 Best Westerns, and checking the table of contents there are films like the SF films Outland and Westworld and the 2 Kurosawas Yojimbo and 7 Samurai, and at # 3 the author has No Country for Old Men. None of them I consider as western, even if some have western elements.
#1 is btw The Wild Bunch followed by GBU and OUTW at # 5. Other Spags are FaFDM (# 14), AFoD (# 23), Il grande Silenzio (# 27) and Django at #44.
Not bad …