It's all a matter of taste, though. I think JD tastes bad; other people love it. That's fine. I'm not a fan of most cheap blended Scotch whiskys either, but on the other hand, I do like dirt-cheap London dry gin. I'll drink that neat or with mixers. I'm not denying that there are better gins but I feel lucky that I'm happy with what I get at £10 per bottle instead of £40.
I think it depends on the bottle. I'm not a fan of many cheap blended whiskys like Johnny Walker, but I find Famous Grouse to be fine for a cheaper blend, and some of the slightly more expensive blends like the Naked Grouse are genuinely very good! Chivas Regal is also perfectly OK to my palette.
Can mostly say the same for cheap anything, though. Depends what your use is.
Sierra is fine if you're going to mix it with grenadine and orange juice for a Sunrise as the tequila is a background player. But an El Diablo is very tequila forward (if made fairly short with limited ginger ale) and benefits from a good quality tequila.
And for a slammer I definitely want a good tequila as that's what I'm mainly going to be tasting. In fact, we finished off our Xmas bottle of patron gold as slammers last week.
I don't drink many straight spirits, most of them really don't taste good like that to me. There are some whiskies and bourbons I enjoy straight, and occasionally a dark and/or spiced rum, but mostly my spirits go into cocktails. Going to experiment with some sours recipes using the Jack, might tame the sweetness a bit.
I've sampled a few single malts and found them generally pleasant but unmemorable. I think I prefer blended, but maybe I'm just a cheap drunk. My fave going on for a few years now is Islay Mist, allegedly 8-yo and blended with Laphroig.