I like to catch posts before they're popular. Say some silly goose shit in the comments first and either be downvoted to hell or praised to the heavens.
You get in early for discussions. You can catch stuff that needs reporting early enough that maybe someone else doesn't have to deal with it. You catch lemmy trends sooner. You get any news that happens to show on lemmy earlier than you would otherwise with other sorting methods.
Plus, you also end up finding more new communities overall. You can still do that with other sorting methods, but it's much more likely a new one will get buried. And you'll never get that sticking to subscribed feed only.
Beyond that, the new sorting feels more organic, more alive because it's flowing in the same time reference as you. It isn't putting things in front of you because other people and some computer fuckery made it that way; it's coming to you roughly the same as it gets posted.
It comes with drawbacks, but it's still my preferred sort.
I run an instance by myself, so I tend to default to "new" mostly to catch spam and shit early and axe it.
On my LW account, I tend to stick to "Subscribed" unless I'm looking for new content to subscribe to. I also block a lot of communities and pretty much all bot accounts because of exactly what you listed in the post.
I only sort by new for my subscribed feeds. I feel it works really well there. I rarely go so all or anything like that. Too much unwanted stuff for me personally.
I'll often browse Lemmy by Top 6 Hours or Top 12 Hours, depending on when I last checked, and if I get through all the posts, I'll start browsing via 'New' sorting...
Now, not really. In the future, I expect subscribed new to be more important as content becomes more abundant and there might be a point where you could miss out on posts that didn't see the kind of engagement to make it on your stream.