No, not all riders disagree. Pecco does not and even Marquez does not! Also, many riders are being political while talking about the subject. Crutchslow's opinion and .... have no difference. Riders are just riders, nothing special with their ideas.
And I'm not hoping MM goes slow. I actually liked and praise his courage to move to Gresini and hope he gets well, but it won't a be piece of cake by no means. If you pay some attention to what happened to Rossi after Ducati fiasco, he took quite some time to begin being fast again on the M1 and that is a bike Rossi knew every bolt. And there is no reason to believe with MM will be any different. Topping Valencia test times means nothing as many riders go super well on these tests but do poorly when the season starts, but I cast doubt about MM topping the rank in that test. Testing is testing, racing is racing. He will get to learn how to setup the bike (Desmo16 is know by its complexity), get used to his new team and mechanics and engineers, learn how to manage the tires on the Ducati, a subject that has shown to take some time whatever the rider, learn how to take advantage on the new soft tire for a quick shot, etc. A lot of new things.
MM is not a magician and personally I never thought he's done any better than Stoner did (speaking about talent, not numbers). MM will not last forever as the best. In fact, right in 2017 when he was 25 years old, riding a very good package, he struggled to beat Dovi, an average rider, on its top form. Dovi managed to beat him and give him a run in many tracks. So, how fast will be a 31 years old Marquez with a completely new team and bike, against the likes of Martin, Pecco, Bezecchi, maybe Bastianini and the Aprilias growing?
I'm not talking MM won't be competitive, he will, but fight for the title is another totally different matter. Take it easy. Be aware for not getting into big frustration mate.