For 1980's->1990s. Curved CRTs are the best way to go.
I agree, I think it adds a certain element of physicality to the display and it's also more authentic to the time, but I understand why people don't care about that either. I also think maybe I'm alone about the physicality thing, but feel free to agree with me.
Scanlines in no way replicate the look of an actual CRT. On my LCD I have filter turned off, "unevenstretch" disabled on MAME and all my games are set to "Pixel Aspect" under Video Options. I think this is the best option if using an LCD monitor, because it only stretches the image by a whole number of pixels eliminating any weird upscaling artifacts and it isn't at all blurry from the filter setting. The disadvantage is that the output from some games (like CPS games) aren't even close to 4:3, but at least you're correctly seeing the video as the game sees it.
Scanlines are useful if you're using a large computer monitor that's right up to your face, because the image then is gonna be too blocky to even comprehend. This is why:
https://www.shadertoy.com/view/XsjSzR#And if you're going through the trouble of converting to/building a MAME cabinet, don't go LCD if at all possible, you're only cheating yourself...