was because it was done behind people who didn't care,
I think this is also the second biggest problem in the adaptation scene. Henry Cavill recently bailed on The Witcher because the showrunners didn't give a fuck. It's the same shit time and time again, wannabe hollywood types use a popular franchise to make their own dogshit which then ruins the franchise they were supposed to be making a faithful show/movie of in the first place.
But yeah, most of the people making these things don't actually give a shit about the video game or even property they are adapting. If you don't care, then you are not going to produce anything good.
And let's be real here for a second, the reason why things like the Sonic movie did good was because it didn't try to be the video game and was just it's own goofy fucking thing that mostly worked because Jim Carry is awesome. Furthermore shows like Arcane work because they are little more than character stories using established video game characters. League of Legends doesn't have much of a story for it's fighting so a show based off the lore is easy because the audience can't connect a lore film to a gameplay one.
The Arcane thing would work fairly well if they did the same thing with something like Street Fighter, hell the Street Fighter anime proves that true. However that same concept doesn't work in something like Resident Evil or Tomb Raider or any number of other flops. Some games succeed because they are games, not in spite of it. And the removal of the game element to the work does not carry over well.
There will always be the rare exception, but you have to look at why the exceptions were good in context because that will tell you exactly why the general failure is consistent.