Why can't I add my own homemade recordings to my apple music ?

You can't sync music through iCloud Library unless you have

• An iTunes Match subscription, or
• An Apple Music subscription with the Sync Library feature turned on

Even then, you might not be able to directly transfer recordings from Voice Memos to Music on the iPhone itself.

If you don't have a subscription, or if you deliberately keep "Sync Library" turned off (as I do), you can probably

• Transfer recordings from Voice Memos to your Mac (using manual synchronization)
• Add the recordings to your Music library on your Mac
• Synchronize the music from your Music library back to your iPhone's Music library – using iTunes Match, the "Sync Library" feature of an Apple Music subscription, or manual synchronization (as appropriate). The third method woud not involve "iCloud Music Library" (which pertains only to the subscription services).