>>42429197The gen 7 metagame was extremely matchup-focused. There were a huge number of threats running around, and it was impossible to prepare for everything with one team. It was too common for a ladder match to be decided at team preview; one person just instalost because they didn't have the means to deal with one of the opponent's mons.
The metagame was considered to be unstable by many. The amount of volatility was undesirable. One way to ease the pressure was to use glue mons - pokemon that compressed roles and dealt with multiple threats comfortably, and let you have a few free spaces on your team for other things. Landorus-T was one of the best. It could comfortably check a bunch of top threats while doing lots of useful stuff (i.e. not a passive deadweight wallmon).
The hate comes from people that don't know what they're talking about. They see Lando all the time and are annoyed by it, they see the high usage and reason that it must be bad and broken if it's getting used so much.