I have custom skins and eyes in my game that work fine. You don't say what you've done, so I'll just lay out how it's supposed to be done. First, make sure they are from sources where you can see file information and comments from people who've downloaded and used the items. Sometimes something will come up in the comments that explains a problem you end up seeing. I almost exclusively use Mod the Sims and More Awesome than You. Occasionally Boiling Oil.
Make a downloads folder inside the Legacy folder. Make sure the files you are wanting to install are package files and not something else. Sometimes they are compressed and need to be opened with a zip file opener like 7 zip. Then you can either boot up clean installer and use it to install them or just drag them directly into the downloads folder. If you use clean installer, you will need to change the file paths it is looking at because it hasn't been updated to default to Legacy. (clean installer can be downloaded from Mod the Sims).
Most of the time I just drag the files into downloads myself (but I'm very, very picky who I download from). I use clean installer if I want to pick and choose from all the files the creator included. For example, if they included hundreds of contact colors and I only really want a handful. You can see them all and check just the ones you actually want.
After you've installed the package files in one of those ways, you need to delete all the cache files and the thumbnails for Sims and the catalogue from the Legacy folder before you start the game again.
Thanks for the sincere reply. However, what I meant was not custom skins or eyes. They work fine in my game too. But when I tried to apply skin overlay CCs, such as body hair and freckles overlays, they didn't appear on any Sims' skin. They're not like a usual custom skin, eyes, or cosmetics, so I don't think your method is going to work, as I already tried that. I removed all previous custom content from the Downloads folder, kept only overlay CCs, and played the game. Still, they didn't appear. I wonder if EA blocks this feature in Legacy Collection, as it worked fine in the Ultimate Collection and CD versions :(
Anything that is CC or mods in Sims 2 is installed in the same manner, regardless of type. As far as I know, they haven't specifically coded any kind of CC or mods out, but Legacy has been updated a few times, and we all know updates can make CC and mods stop working until/if the creator updates them. Some overlays don't work with custom skin or cause weird graphical glitches when used together, but you said you tried the overlays by themselves and they still didn't work. So my guess is, unfortunately they were broken somehow with an update. Maybe a particular game mechanic they were tied to that got re-coded slightly.
I'm sorry they aren't working. I had some clothes and hairs that stopped working with Legacy, it's a bummer.
