How do you make peace with the randomly generated sims?

I have finally left them in the unplayed area with neighborhood stories disabled.  Thankfully, it has worked so far. I am playing in a royalty save, playing only one family right now.

I am still trying to learn to live with this. I made a good amount of Spellcaster NPCs to minimize/stop them generating when I got to the Magic Realm (this really helped). I tried to download extra Maxis produced Households for not in world NPCs but still the auto generation madness won't stop.

I feel bad because my game seems to be stuck in 3 types of favoured auto generation preferences. Asian looking dominating facial features (which I do not mind having Asian looking Sims, in fact some of my favourite NPCs I have saved were saved from original auto generated ones, I just re-dressed), dark skinned with blonde/red hair (and not fashion looking, like uncomplimentary contrast/colour clashing) and extremely overweight/obese Sims (I do not mind occasional curvy or even overweight, but obese bothers me though, I mean the Sims do not have anorexic Sims (thank gawd!) as that is mental illness, but extreme obesity is also a mental illness, and just as triggering.

That is just the aesthetics, don't even get me started on the fashion clashing and accessory abuse!

I do not want to download a mod (especially script based, tuning mods are not such an issue) to fix something as large of scale as auto generation, as it seems just as much as an upkeep, and potential to break the game in an update.

I just wish the devs would update NPC generation pools where we can do it at the manage/edit world level, like marking an NPC a maid, mailperson, firefighter, bar tender, etc. And if we do not assign, it will be auto generated.

I'm not bothered about townie sims appearance or fashion, but about the fact that they get generated at all. Doesn't matter what you look like, dear pixel, you're stealing the spotlight from my ~100 curated custom townies, who could have appeared instead of you. 
I tend to go on deletion sprees either at the end or the beginning of a game session.

I am not the generational player, so I may not face the same issue with you, but I did a lot to control "random townies".

As you mentioned about using mods, I will suggest the solutions that I use to prevent most of the random townies' generation. You may already used some of my methods, or some didn't work for you, but I hope that some are what you can use for your game.

1."Townie Overhaul Less Fame"  mod, by sims4me at CurseForge.

This mod series will make your game mainly use existing Sims instead of creating new ones.

There are many mods from the base mod and modules in this label. You don't have to use all of the modules. Just use it for what kind of random townies you want to get rid of the most. For example, there is a module to prevent "bar regular".

Note - As this mod is made for Get Famous, most of them need the "Get Famous" EP; otherwise, it won't work properly. For example, no existing university student will arrive if having the mod but don't have Get Famous. Also, the San Myshuno's festival will be empty if not have Get Famous.

2. Using MCCC's Using Tray Sims

If you can have many of the sims that you want to fill the world instead of an ugly one, you can add the #mccc_include tag to many of sims. Then go to ---- MC Population>Populating Settings>Import Tray Settings. Set to import 100%, and no more random sim in your game.

I currently use this setting -- let the game choose my prepared NPC sims (that I add mccc_include tag)-- so no ugly random sims during play, just only sim I prepare in nccc_include -- when I finish the game session on each day, I delete them without hesitation because they will still be at my Library, waiting for use in the future.

Note - Remove this mod before the start of official "Events" such as recent "Lost Legacies". If you don't do, the Event NPC sim will get the tray sim looks instead of the original one.

3. Rebalanced Townie Generation for Sulani, Mt Komorebi, and San Myshuno (by Enkidu, download at Mod The Sims or CurseForge)

This mod didn't stop random townies, but prevented "Too many Asian/Exotic townies". By default, the game generates local sims to fill specific worlds such as San Myshuno, Sulani, Mt.Komorebi, etc. Even if you never visit those worlds, the game will prioritize those nationalities every time it made new NPC.

I think this mod will help you prevent your world being Asian community over time.

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Lastly, if you don't have Get Famous, the game will make new random sims to fill the NPC role. But if you have Get Famous, the game will choose unemployed sims to fill the role.

More short advice that I knew from other players...

Manually fill your game with your sims enough so that the game won't need. You may design sim yourself or download from other players in the Gallery. At least those sims won't have ugly random townie fashion.

You still need the mod to prevent new bar regulars because the game still makes new ones even if you have hundreds of unemployed sims.

Weirdly complected pear-shaped people with wacky hairdos and random outfits offer the useful service of providing folks that my own sims look better than. 

But if it's a recurring presence, I'll have a sim in the Style Influencer career offer a makeover. 😅