First off - we stayed at the Swan on Marriott points a few weeks ago and it was very nice. It was NOT my previous Yacht Club

BUT it was acceptable to us, and I think we will be back due to my enormous stash of Marriott points (we have over a million currently). A 5 night stay at the Swan (w/ the 5th night free benefit) will cost you between 160k and 240k points.
As far as how to earn a bunch of them... well that's not as easy as it used to be. Back in the day, Chase had a full lineup of Marriott cards and Amex had a full lineup of SPG cards and you could get all of them! So some people (like me) still have a large stash of Marriott points from pre-merger. I earned a bunch from getting the SPG cards at all-time high bonuses and then they transferred to Marriott at 3:1.
Since the merger, the card lineup has been trimmed slightly. And there are numerous eligibility restrictions to navigate. Basically, it's way harder now than it used to be to earn a LOT of Marriott points quickly.
Here's this super simple (sarcasm) chart to figure out if you're eligible:
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EDIT: Better Charts added.