I disagree, respectfully of course. Darling in the Franxx gets a bad reputation because of the bad ending arc, at least that's the most common excuse I've heard. I truly believe a good majority of the content before that is fantastic. It has it's dips with a few of the plot points and character arcs but it definitely isn't hot garbage like everyone says it is. Great animation, stellar voice acting and soundtrack, and a good majority of the characters grow in a believable and well written manner. Even the final few moments of the show after the space alien stuff where we see their souls drifting off towards Earth is really well executed. That's why I think it's so great and maybe you should give it another shot.
Not gonna lie, I feel some hardcore world war stuff has been really under used. We saw in the opening episode of the Final Season of Attack on Titan that a World War 1 like setting can really work in an anime format. A dark, gritty, and historical war story is something that not a lot of shows have really touched on and I feel there's so much untapped potential there.
Mecha is fantastic right now, but only if you're already an existing fan (this is especially the case for Gundam). In the past few years Gundam fans have gotten Unicorn, Thunderbolt, Narrative, and Hathaway which are fantastic, but they are only good if you've gotten caught up with the forty years worth of source material which isn't ideal for new fans. Iron Blooded Orphans did come out in 2015 and it is also great, but it just didn't make waves like Sunrise thought it would.
Then you have other series like Full Metal Panic! which got its fourth season after 12 years back in 2018 which again was fantastic but there's still a decent amount of source material to get through to really enjoy it. Also in 2018 you had Darling in the Franxx which I personally loved but I'm definitely in the minority with that one. I can totally understand its flaws and why it was a real turn off for a lot of people.
Overall mecha is as strong as ever for me, but it needs to start appealing to new fans if it wants to survive. Plus it needs to not trip over it's shoelaces like Franxx did to keep people engaged. Hopefully AMAIM: Warrior at the Borderline or the new Mobile Suit Gundam: The Witch from Mercury coming out will be newcomer friendly.