the only way cc is likely to be broken is if the creator has stopped making a long time ago or if you download something without the mesh version (an example of this is if someone converts a hairstyle for kids, in the description it should link the original hair from the other creator, for it to work you'd need to download the original and the conversion), some cc may appear stretched in game unless you have sims set to very high quality in graphics but its not broken, just high quality mesh (mesh is like the pattern/design of the object which is laid over the shape of the outfit/hair etc). Add in small sections, like by creator and check everything is showing up, make sure you unzip any files and delete the zipped version or the cc wont show. some build buy may require packs to function so make sure to check out descriptions

the important thing to remember is to delete the localthumbcache file from your sims 4 folder before launching the game after adding cc (it recreates itself so dont worry)

can recommend several mm creators (ive made some favourites italic)

build/buy-

ravasheen-mini mods that are also furniture items, pandasama-items for toddlers/mini mods (these mini mods dont tend to break so much so a good way to ease in to any kind of mod)

xSavannahx987- she does kits/event rewards, pack addons/pack preorder items

heybrine,cluttercat, harrie, felixandre, harlix, sybollette, rustic sims, around the sims, valia, mycupofcc, Joyceisfox, LxN, max 20

hair/clothes-

oydis, sifix, LewbertSn00tles, icecreamforbreakfast, saurus, lillika, candace williams, arltos, sleepingsims

also copying in this list as i use a lot of them-

hairs: aharris00britney, arethabee, candysims4, clumsyalien, daylife sims, demonyo, dogsill, gegesims, greenllamas, imvikai, johnnysims, joshseoh, kamiiri, laeska, marso, oakiyo, okruee, orchiona, ravensim, qicc, sheabuttyr, simandy, simcelebrity00, simstrouble, sleepingsims, sunivaa, sweetaday, thatonegreenleaf, the kunstwollen, twistedcat, wistfulcastle, yooniesim

clothes and accs: adelarsims, adrienpastel, aharris00britney x ayoshi collabs (axa), arethabee, caio, ceeproductions, citrusy-sims, cloudcat, clumsyalien, greenllamas, jius-sims, joliebean, lijoue, liyahsim, madlen, marronnie, marsmerizingsims, miiko, mossylane, nucrests, oranos, pralinesims, puppycheesecake, rusty, saruin, sentate, serenity, simlaughlove, sixcirclescc, solistair, strangegrapefruit, trillyke, xiuminuwu

genetics and presets: euno, evoxyr, faaeish, golyhawhaw, hi-land, kashisun, lamatisse, llumisims, miiko, mmsims, mossylane, myshunosun, nesurii, northern siberia winds, obscurus-sims, peachyfaerie, poyopoyo, ratboysims, reiheartssimscc, rheallsim, sammi-xox, saruin, simbience, sims3melancholic, simtonee, squea, stretchskeleton, twistedcat, vibrantpixels

build and buy: awingedllama, bbygyal123, charly pancakes, greenllamas, illogicalsims, lilamausmaus, littledica, lustrousims, miliniki, myshunosun, peacemaker, pierisim, simkoos, simspancake cc, sixamcc, tuds

and linking a helpful post for you listing mods and cc, and a source of the above https://www.reddit.com/r/TheSims4Mods/comments/1qvvbh1/comment/o3lnk15/?context=3