If someone plans on playing the whole series then yes, start with DS1. But if they just want to pick up a game and heard Souls games are really fun, I don’t think the first one would convince them to check out the rest of the series unless they really enjoyed it, and I think later games are more approachable for beginners.
That’s totally fair, it’s not for everyone, and that’s okay. It used to be my favourite game ever, and is probably my #2, but I find it difficult to recommend to a lot of people because it is definitely a steep learning curve and is even harder if you’re used to Dark Souls. There’s no dodging (well there sort of is but it’s more of a repositioning) and instead you need to rely on parrying everything. And like you said, there’s no gimmicks or anything, you simply have to get good at the very specific playstyle or you won’t have a good time. But if you do get good at it, it feels amazing to play. Just out of curiosity, what pushed your limits in DS3 and ER?