This isn't my transaction. I'm just seeing it on mempool dot space and trying to understand why it's not being propagated to my node.

My guess is that you need to rebroadcast it. (I might be wrong)

Your node mempool was full when you broadcasted it. So, it didn't reach your node.

Now your node has space, but nobody is broadcasting your transaction anymore, as it was broadcasted long ago.

Try to rebroadcast it here:
https://www.blockchain.com/explorer/assets/btc/broadcast-transaction

If you don't have the raw transaction, you can get it here:
https://bitcoindata.science/bitcoin-raw-transaction-hex

or here:
https://mempool.space/tx/***your tx id*** then, look for raw and click it.