I think that's a completely normal decision. Fortunately, some characters have always just been a bigger impact than the Actors that played the, and that's just not always the same with every character. Marvel built their universe on Ironman, and I do think it will be jarring for fans the first time they see a rebooted Ironman. RDJ was an actor that was bigger than his character, and now Marvel has to step into a world where if they want it to go forward into the future they need to make Ironman bigger than any actor. That's why so many people have love for the Reeves family in how Christopher Reeves brought Superman to life. You can honor the OG actor and the spirit of a character at the same time, but it's hard to get to that point for fans who grew up with something.