I don't know, Mirage...I opened up the mission to remind myself what it was, and am now skimming, and I keep laughing aloud at bits. Things like "okay, so Elrond and his canonical kids have green hair, then?" and the concept of Elrond ruling all the Elves in Middle-earth with, apparently, no objections from the people who likely would object (including Elrond himself!) I'm familiar with that feeling of suddenly realizing that your older writing isn't quite your style anymore and trying to move forward without entirely being sure how to do it; in my case, I found my writing style had changed and I wanted to write new things rather than continue the old, but was struggling to come up with new ideas and sustain confidence in their quality. The solution has basically been...time and self-reflection and continuing to write this and that as I figured out where to go? And then the ongoing situation upended things a bit, including writing-wise, and I adopted a policy of "write anything that interests or amuses you even if it's very silly" because, well, I spent a good bit of March and a chunk of April barely managing to write anything at all (going into lockdown and having to suddenly figure out how to order everything online and generally just reshape most of how you do things will do that, as it turns out). At this point...I'm not entirely back to what I was doing pre-March 2020, in large part because the themes of my original fiction project of the time still don't quite appeal to me in the midst of all this, but I'm more in the stages of "let me finish up some of these things I began last year and share them, maybe" than "write whatever new idea shows up and amuses you". And...behold more self-reflection, I guess? Though the type I was talking about earlier was more to do with slowly analyzing how my writing style had changed and using that to try to start building new ideas. Anyway. I think the point of this was to say that I sympathize, and to share my version of it in case there's something helpful there? (With a little detour into "hm, where am I at in 2021, this is useful information for me"?) I don't know. It's early. Hopefully you got something from it.
A more specific comment, for fun:
Apparently he had met the Sue at an archery contest some decades ago, since she was as talented with a bow (of course) as any elf or god.
“Ah, yes, all those gods roaming the streets of Middle-earth,” Melissa said, and May chuckled.
I am quite likely repeating a beta comment, but hey, I suppose Maiar could potentially be considered gods? Demi-gods? Although, uh, I just can't see most of them taking an interest in archery. I mean, Gandalf and Saruman facing off in an archery contest would be hilarious, but I can't see it happening. Perhaps she's just bringing in the Valar--if I remember correctly, Tulkas and/or Nessa might have something to do with hunting/war that could include archery?
Anyway. Overall, good luck, Mirage :) It may be frustrating right now, but it's always good to grow as a writer (and, iirc, age-wise you're around a time when it tends to happen, so you're not alone. If anything, you're probably following in grand tradition!). I doubt your old writing is as bad as you might think (even if you've reached a point where it makes you cringe), and I'm sure you'll write great things in the future. Just keep at it! :)
PS: I gave the rest of the mission a quick (re)read too. I can kind of see what you mean (possibly down, in part, to beta comments I would make note but possibly didn't think of at the time?), but at the same time, I did keep laughing out loud. "Iniih - the sound a horse makes?" got me, for instance, and the writing quality itself is fine. Most of what I was tilting my head at was...pacing, a bit, and what feels like some missed opportunities for analysis/remarks about canon. Maybe there could be more description of the agents' general movements/interactions with their surroundings? Though that might just be a casualty of semi-skimming.
Anyway. I can see why you might now feel there's room for improvement, but you really aren't starting from nothing, especially with the comedy. Do some reflection, think about what you want to change/enhance (or what already has changed!) about the way you write, and I think you'll come out the other side stronger. Quite possibly you're already emerging. Either way, I think you'll be okay :)
PPS: Also, it's very much okay to scrap a bunch of stories! I've done it a number of times, including but not limited to an entire arc for Jacques (the concept got thoroughly reworked a few times and then made kind of obsolete; the current plan is to fold the characters and some pieces of the plot into what replaced it, I think) and just about my entire planned first set of ~5 missions back in 2013 :D I had a plan! It was going to use my permission piece characters and everything, and introduce others as I went! I had fics and a timeline and everything! And...then I think I went off and started writing a bunch of stuff for Dawn, or something like that, and RL took over my timing, and then I brought the Reader in earlier than planned, and, well, suffice it to say that there's a whole set of events planned for 2013 that will never be written. Although, now that I'm talking about it, I'm a bit curious to see if it could maybe work folded into an interlude, maybe fill in some more pieces for Brenda and Charlie (don't recognize them? That was my permission pair and I had plans, I tell you) and probably also Edgar and Agen----t and Dawn...hmm. We'll see. Not a priority, though, given I have other stuff I'm finishing/trying to finish. Anyway, tangent aside, scrapping missions happens, and can even work out for the better. If you're feeling guilty about it, or something, there's no need :)