I really don't know why so many people speak so poorly of this game. The world is massively huge. The different javelins provide you with distinctly different play styles. The combat is usually intense. It has great voice actors telling an interesting story, with the promise of much more to come.
My only issues with this game are:
The Interceptor and Colossus javelins fall off quickly in terms of power, compared to the Storm and Ranger. Bioware definitely needs to do some re-balancing there. That said, I switched from Interceptor to Ranger and got everything I wanted for my play style.
Early game you receive far too much loot. You are constantly changing out large parts of your gear for something better. This makes it difficult to play with your builds. This falls off, however, and by late game you can go whole days of play without finding a better piece of loot.
I find crafting to be too simple. I would also like to have direct control of the stat bonuses the gear provides.
Many of the stats in the game are a mystery. The game, in no way tries to explain them. That said, a quick Google search can answer all of your questions, so its really a minor annoyance.
That said, I find this game challenging and entertaining. It's basically Destiny 2.0. I can only assume most of the hate comes from Destiny players not wanting to admit how much their game sucks.
I've had more fun (and spent more time playing) with this game than any since the multiplayer of Mass Effect 3. Ironically, its the first game I've bought from Bioware since Mass Effect 3 as well. They really pissed me off there, but that's an entire different wall-o-text.