This info is from MARA:

"Is my transaction guaranteed to get mined by Marathon?
No. Once accepted by Marathon, your transaction will compete with other Bitcoin transactions for inclusion into a block. You will receive a personalized link to view your transaction's status."

If I solve 67 I'll try Mara, but the more I look into the topic I believe less in MARA. The question is it the only solution? Or is it hopeless against the BOTs, if so then you shouldn't waste your time/money on 67. But I'm not an expert