I think it’s irrefutable that 44 gets far more stick than any other driver in F1 has, including MS. Senna was a god, that happened to drive one of the best cars ever produced. Same for MS in parts at his time at Ferrari. Mansell drove possibly the best car to win a WDC too. If Brawn had the moolah, Button would have absolutely dominated 2009. Show me a WDC and I’ll show you the car advantage he’s had 99% of the time. I’d say the close racing in a lot of the 80’s left me looking at which was the best car and being confused, but not towards the latter part. Rosberg’s car is the only car I think that wasn’t the quickest, best car to win a WDC back in the day, but my memory fades.
As for equal cars and equal drivers, I read Williams say sometime in his life, that if you chucked any competent F1 driver in a car, and they’ll lap within .5 of each other. That’s why they paid for the ones that were at the top of that .5 gap and it’s those who make the difference. As an aside, and OT, the Renault boss (Fauvre?) who provided the V10’s for Williams during what I think was Newey’s heyday stated he thought Mansell was the quickest of any driver he had, including Prost and Senna. He said if he went out and did two qualifying laps, and one was slower, you knew it was the car.
I did write an extensive answer to this, but frustratingly Chrome crashed and I lost it all, sigh. You would have been amazed at the pithy insights and irrefutable arguments, but you'll just have to take my word for it 
The abridged version is that Schumacher did and still does get an awful lot of stick. Many people claim his success was all down to the car and the fact he had a team that supported him 100%, that he never had a team mate worthy of the name, and that he only had success because all the other drivers were rubbish (paraphrasing here). Most of these are either from people with very short memories, or ones who never actually saw him race in his prime, but regardless he still comes under fire for the above even now, and these excuses are inevitably rolled out whenever comparisons with Hamilton are made.
The internet has changed things, too. Back in the day there simply wasn't a medium to discuss and compare drivers like we do now, and every driver act wasn't analysed and discussed to within an inch of its life. Drivers are more accessible than ever before, and with that exposure comes a lot more commentary. But Vettel used to get a lot of flack, and his name was barely mentioned in his WDC years without the "Newey rocket ship" tag attached. I think many people thought that was his middle name. Again, his success coincided with greater forum activity and accessibility, so debates raged on a daily basis. Hamilton, too, is enjoying success when every man and his dog has internet access, and with success, particularly prolonged success, comes inevitable discussion.
I do recall Mansell in particular getting extensive criticism, however, even allowing for the lack of readily available medium at the time. He didn't help himself with his "me against the world" attitude, though, and nobody really likes it when a successful person claims adversity, especially when it's obvious to everyone else that they have enjoyed a big advantage. Even when he'd lapped everybody else by the way he talked in the post race interview he was valiantly battling the odds and holding the car together with hastily cobbled together rubber bands etc, winning in spite of the car. It tended to wind a lot of people up, so they looked at ways to bring him down to earth again. Credit was almost invariably exclusively his, in his eyes, and he certainly struggled with the concept of winning graciously.
I think the greater the success, the greater the chances that people will find something to criticise. Despite what I said about Mansell, only partially tongue in cheek, it really started in a big way with Schumacher, probably because people were looking for ways to explain away the almost unprecedented success he had. The next dominant driver was Vettel, and he got lots of negative press during his WDC years, and then of course we have Hamilton, who has enjoyed even greater success, so he naturally becomes the next target.
And, similar to Mansell, he attracts criticism at least in part by his own attitude and actions. If you style yourself as fighting against the odds, then it invites criticism, especially when those odds aren't all that visible to people. He gets involved in noble causes, which is admirable, but sometimes the way he does can give the impression at least that self publicity is the aim. That may be unfair, but it is part of his image and certainly one reason why he is a target for some. But in all honesty I don't recall him attracting anywhere near as much negative attention before his Merc days, aside from the obvious things like Liegate, which is largely self-inflicted anyway. Continued success will always attract scrutiny, that's all, and I don't see him as being excessively put-upon.
Regarding Williams, Frank was notorious for being fairly dismissive about drivers and what they brought to the table. He was famous for not paying much, comparatively speaking, and for firmly believing the car was the star. I'm not sure I'd fully agree with him, tbh, because most of the giants were giants precisely because they stood head and shoulders above even their team mates, and in any event in those days sizeable gaps were not that uncommon. Of course they need a good car to be able to do anything, which is why Alonso isn't nipping at Hamilton's heels just now, but we can see from the difference between eg Hamilton and Bottas, and Max and Perez, just what a top driver can do, given the opportunity.
I expect that Merc will still be top next year, and would be hugely surprised if they weren't at least extremely competitive. I hope we don't go back to peak Merc, because I've really enjoyed this season for the most part and I'd hate to go back to another processional one. And although I've little doubt that Hamilton, like most drivers, would enjoy having the undisputed best car, as long as it's good enough I think his intensely competitive nature will give him the motivation to prove himself again. He needs a realistic chance of winning to deliver his best performances, IMO, but if he feels it's there he will fight all the way
