Does iCloudPhotos have any metadata for the photos uploaded to it?

Apple does not give any reason for this. Probably it is limited because the web page has to be compatible with all kind of browsers and platforms, so it is limited to the bare necessities.

Until iOS 15 / iPods 15 came out, the only platform where we could work with metadata at all has been Photos on a Mac. Photos at www.icloud.com has been limited to what Photos could do on the iPhone and iPad. It is only recently that we can tag our photos on an iPhone or iPad with titles, change the date and time or the location. It would be great if www.icloud.com would be updated as well.

You may want to send a feature request to Apple with the feedback form: Apple - iCloud - Feedback

All metadata you add on a Mac are saved in iCloud Photos. The web page at www.icloud.com is just not showing them.

But I can see on my five Macs with different system versions that the metadata, adjustments, albums, folders I am adding on any Mac are syncing with iCloud Photos to my other Macs and I can see them there. To convince yourself, you could test this by creating a second user account and download your iCloud Photos Library to a new, empty library on an external volume. All metadata should be there. (you need the second user account for testing so you do not have to switch iCloud Photos to a different library in your main account, because this would result in a new lengthy upload of your current iCloud Photos Library).

Or, if you have an iPad or iPhone syncing with your iCloud Photos Library, search for a keyword you have assigned on your Mac. The iPhone will be able to show you the photos within keyword, even if you cannot see or assign keywords on the iPhone.