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.
-----------------------
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.
