Welcome, Least100Seraphs. I sympathize with your question of recommendations because I struggled with that myself when I seriously startes getting back into anime a little over a year ago. I'd missed out on a whole decade of shows, so trying to decide how to get back in took a few bold leaps, but I feel my time has mostly been well spent.
Judging from your list, I gather the things that you gravitate to have either excellent animation (over say, a distinctive artistic style) and/or strong, character-focused writing (as opposed to sweeping plot-centric shows). With that in mind, here's a few personal recommendations, with a couple notes about them given I'm not certain what your limits for certain types of content might be.
Fate/Zero
I doubt I'll be the only one to recommend this, but it's still one of the best "shounen battle" style shows around, and arguably the best introduction to the Fate franchise. It's "realistic" take on the Holy Grail War is a sight to behold, not only as it tells a fantastic tale on its own, but how being a prequel to the very different Fate/Stay Night doesn't cause it to feel any less well-realized as its own entity. A word or warning, though: this is a brutal show. Exceptionallg violent, unrelentingly nihilistic, and home to some of the most awful characters I've seen in some time, it's not for the faint of heart. If you're okay with that, though, you'll be treated to an exceptionally animated, throughly enjoyable battle royale.
Ghost in the Shell: Stand Alone Complex
Given your love for Astro Boy and your familiarity with famous '90s sci-fi anime, I imagine you know of GitS. But if you haven't seen Stand Alone Complex, I think it would be worth your time. Structured like a classic police procedural, with some episodes tied to an overarching plot and the rest as stand alone, character-focused one offs, the show excels at challenging a lot of assumptions we might have about how we relate to each other in a world where everyone's brain is constantly online. It's one of the few sci-fi anime that only seems to get more relevant as we close the technological gap with the future the show presents. That said, your acceptance of the Major and the way she interprets the world (and whether or not you see it as nothing more than fanservice, which is a somewhat understandable point) may impact your enjoyment. Still worth a shot, though.
KonoSuba
Comedy is something in anime I find either works really well or falls completely flat. KonoSuba is one of those shows where everything just clicks into place, and as such it becomes greater than the sum of its parts. Now caveat: I've only seen the first season, but this is still one of the best comedies of the last few years because it utilizes archetypes so well in constructing its scenarios, which always save that punchline they've been building right foe the very end of the episode. Now, I will say, if you haven't seen much in the way of Isekai stories up until now, you might not get as much enjoyment from KonoSuba because you might not get as much from some situations as others. That and there is soms pretty explicit fanservice in some scenes (used for comic effect, of course, but its still there). I feel it's worth it, though, because it's so incredibly funny.
Mushi-Shi
Chalk this one up on the "everyone and their mother is going to recommend it" board, but truth be told, there just isn't much out there like Mushi-Shi. An episodic show that focuses on a different cast each show as the traveling Ginko wanders into their lives and proceeds to deal with their unique interactions with Mushi, a divine group of organisms, Mushi-Shi's a tranquil and reflective show that examines interesting relationships between people and the living embodiment of fate, all against an eternally rustic picture of rural Japan that feels exceptionally timeless. It's a real treat, even if it is exceptionally slow and melancohlic most of the time. Definitely watch at your own pace; it's not a show to be marathoned.
Please Tell Me! Galko-chan
This is probably the entry on this list that will get the most eyebrows raised, but I think this is one of the better shows of the last couple of years. It's a series of 10-minute shorts about the titular Galko-chan and her high school friends discussing feminine issues in a very 4koma fashion. What makes this show different is that Galko-chan is not a characture; rather, she feels like a real person. You can't easily put her or most of the cast into easily predictable roles, which makes the comedy feel fresh and have some semblence of meaning when the show tackles issues like ostracism, body shaming, the trials of puberty, and so on. It's a funny show, yes, but there's real grit to it as well that comes from someone who isn't relying on stereotypes for easy laughs, which is commendable.
Anyway, just a few recommendations. Whatever you choose to watch, hope you enjoy it.
