Agree with you on both points to an extent.
However I don't think it can be underestimated how badly Corbyn's lack lustre campaign and frankly sudden switch against character influenced the core Labour electorate. He has always been Eurosceptic, his failure to hang his hat for so long and then subsequent refusal to engage with the campaign he allegedly agreed with was massively damaging.
I like Corbyn, and until today would have voted for him in a GE. His stubbornness (no surprise given the causes he has backed throughout his career) coupled with the fact he has alienated working class people in Labour strongholds like the SW valley's is a very bad sign.
Johnson was never going to come in for any flack from the media. He is one of them after all, he is a journalist first and foremost. He has press backing in a way Corbyn could only dream of. Though, if Corbyn's public character is anything to go by, he positively relishes the unpopular position he stands in.