## It depends ##

D&D 5e uses the natural language meaning of words, unless contradicted by a defined game term. Benefit is not a defined game term. 

Benefit, under the normal meaning of the word is:

> an advantage or profit gained from something. 

Being able to change spells is contingent on completing a long rest. 

The Rakshasa's curse reads:

> The magical curse takes effect whenever the target takes a long or a short rest [...]. The cursed target gains no benefit from completing a long or short rest. The curse lasts until lifted by a remove curse spell or similar magic.  

### Is being able to change your spells an advantage or profit?

In this DMs opinion the answer is yes. The creature would gain an advantage or profit by being able to now cast remove curse (and thus remove the curse). As a result the creature is unable to prepare remove curse specifically (or greater restoration). 

As to other spells and their preparation, that's where the "it depends" comes in. It depends on your DMs answer to this question. If they think swapping one spell out for another would be profitable or advantageous, then no you can't. If however they don't then you can. For example, swapping out Cure Wounds for Purify Food and Drink can be advantageous in some circumstances but very disadvantageous in others. In the good scenarios they cannot swap it out, but in the bad ones they can. 

### So is the party out of luck?
No. Not being able to remove the curse themselves is a pretty dire situation and would, for me as a player, result in returning to whatever safe haven is nearest to enlist the help of whatever cleric, druid, or other spellcaster that could cast greater restoration or remove curse on me. I would be explicitly disincentivised from doing any further adventuring. 

Your cleric also has the option of trying their divine intervention feature *every day* until it succeeds. After 7 days of repeated request, at 16th level, the cleric would have a 71% chance of success in asking their god to intercede on their behalf. By 20 days they would have a 97% chance of success. 

As a DM, this situation is an opportunity to provide the players with a social and exploratory pillars of the game. At level 16, the party will, almost certainly, have accrued favours and goodwill from the great and the good of the land. This situation is the time to *cash them in*. Whats more, the party should, by this stage, have access to fast travel via magic that can put them almost anywhere in the world.