It's harsh. It's also true.
If the OP had bothered to do any research before plunking down thousands of dollars on airfares (rather than just making assumptions that a particular set of circumstances exist, like that airline bookings work the same way as hotel bookings), they would have seen hundreds of complaints and warnings about Gotogate and booking flights through Booking.com. The OP's post merely joins those ranks.
Likewise, they failed to check their booking after it was made with the airline (again making more assumptions that Booking.com had made the booking correctly with MH with the correct luggage allowance).
(The observation about Tripadvisor is more that its Air Travel forum is filled with people complaining about the 'scams' of online travel agencies when their desire to save a few bucks compared to booking directly with the airline has blinded them to the risks and complications of using online travel agencies - risks and complications that could have been avoided by doing even the smallest amount of research before booking, rather than just clicking on the lowest price offered by Kayak or Skyscanner.)
