Sadly similar to Metallica, In Flames decided to "move forward" in their music and cater to a "wider global audience" thus scarifising their original melodic death genre.
Their works prior Reroute to Remain, IMO, are definately classics and are source of inspirations of many metal bands here and abroad. I can honestly say that I am heavily influenced by Stromblad's guitar playing and it was In Flames that became the catalyst which got me started to playing and exploring this metal genre.
Ignore their later releases first and listen to Whoracle, Colony and Jester Race. There won't be anything controversial about them then...