Well, we can't stand the ToR rules and have been playing this game using White Box so I can't see much issue with converting it to 5e. I think it depends on exactly what people want from their Middle Earth Roleplaying experience. We just want to game in Middle Earth. I don't need a bunch of gimmicky mechanics and unnecessary dice rolls for journeys, councils, etc. to slavishly recreate the books. I'm grounded enough in the lore and setting details that I can create that feel myself without all the rules getting in the way of smooth gameplay. We can roleplay that stuff. Likewise, none of my players, all of whom have basic familiarity with older versions of D&D, have any interest in learning a whole new game system. But I like the feel of the ToR materials and settings, scenarios, etc., are good. It's just the mechanics we don't care for. But we've borrowed a few things from ToR to make it specific enough and add that Middle Earth spin so that the classes feel different. We even found a way to incorporate the feat dice in a cool way.
Not sure we'll bother with 5e stuff since we have our workaround already, but I totally get why they want to tap that market.