Is it a "must" to be informed?
I mean, it helps to have a sense of dimension for the things you love and which fascinate you. There will always be the "I'm intuitive and I don't need to know
anything" school of tarot.
Secretly, I think if someone is really into tarot then owning a RWS is a must, yes - there, I've said it. However, there are people who have one deck and spend their life reading with it - and if it isn't the RWS, I don't think it has any impact on their skill and relationship with tarot. There will be people who have read with the Thoth - for example- for 40 years and don't feel the need for any other deck.
But - hey - we all use tarot for different things. I personally can't imagine really loving tarot and not having a RWS. I can imagine having a book with the images in and refering to it and not feeling a need to shuffle the RWS, but that's different. But I can't imagine a deep love of tarot which doesn't embrace some knowledge of the RWS. You don't have to like or read with it - but some level of familiarity is good, I'd say.
But then the RWS isn't exactly traditional. What if I ask - "can you
honestly consider yourself really into tarot and not have an Oswald Wirth. Or Vachetta? Or Etteilla?" Was it just chance - or perhaps U.S Games - that brought the RWS to the forefront?
ETA
Since it is the Most basic and earliest Tarot Deck
Just seen this! er... NO!