They tried to force a rule change called SegWit2x despite the vast majority of the bitcoin community and network participants opposed.
They don't batch their transactions and dump every single one onto the blockchain, which is basically spamming.
They have been dragging their feet to implement SegWit.
They colluded with Roger Ver to pump Bcash.
They have a huge pool of UTXO's which will cost them more to move than they are worth. SegWit addresses won't help, but a
block size increase would (how convenient then to try and force 2X rule change).
It's technical incompetence on their part.
https://news.bitcoin.com/coinbase-accused-technical-incompetence-hoarding-millions-utxos/