For me personally lack of maps is the biggest reason it gets old. W:ET didn’t have more maps, but they were more distinctive. SD are determined to add more Counterstrike maps, I can’t see it being a huge deal. More like a desperate attempt to draw CS players. Mercs themselves are not very distinctive too.
Also, W:ET had less crappy weapons nobody used. Thomp40, Sten, Garand, FG42, Mortar, Panzerfaust, deployable Mg42, they were all in use. Flamethrower a bit less, but it was fun. Okay, knives were pretty bad.
Just takes some time though