They are getting the OP to their destination. OP just doesn’t like how they’re doing that.

Which is a valid criticism given the lone rebooking option.

Delta is following their rules under their contract of carriage. They have offered a rebooking that complies with the CoC. They legally don’t have to do more than that though they do give their front line employees a good amount of flexibility beyond the CoC to resolve concerns.

But they can’t fix everything. And they aren’t going to buy the OP a cash ticket on another airline unless the OP meets very specific criteria. Had Delta cancel a transatlantic flight for me last month on day of departure and they wouldn’t even try to put me on a Lufthansa flight that day and I’ve got somewhat okay status in the SkyMiles program. (Other SkyTeam options would have gotten me home later than the scheduled relief flight)

The nature of air travel is that Stuff Happens and you aren’t always going to end up with what you want; doubly so since 2020. You either accept what options you do have or you take the refund and move onward.