Season Passes - This one is kind of innocent, really. Pre-order your DLC, and get a discount. Seems reasonable enough to me. The issue comes with the fact that most people don't buy map packs, anyway, so games just tend to revert back to the vanilla content after the honeymoon period, and trying to find a server with DLC content is basically a minigame in and of itself.
Another problem is when the devs put out a season pass, but don't explain what the future content is going to look like. Halo Wars 2 had a season pass, and it said it would "include additional campaign content", which ended up being a mini 3-mission side story. They then went on to release the Awakening the Nightmare expansion, that was, of course, outside of the season pass.
Microtransactions - Little tidbits of content. Buy what you want. So long as it is cosmetic only, I don't have an issue with these, but just like lootboxes, they can be abused to be P2W, and that is where the problem lies.
A lot of companies have sense, and just do cosmetic stuff. That is A-OK in my book. Cosmetics aren't required, but are cool little ways to invest in your character.
Lootboxes - "Pay the same as a microtransaction, and you will get something! Spend $99 for our best value pack!". I don't actually mind loot boxes all that much. I like random. The problem is with the drop rates, and it really abuses people with completionist complexes.
Heroes of the Storm does lootboxes pretty great. You get a lootbox everytime you level up a hero, and that encourages you to experiment with new characters. I have never felt like I need to buy lootboxes, and the drops are cosmetic, free heroes, or XP boots.
Conclusion - None of these options are "bad", but all can be abused by greedy devs. Personally, I would rather have microtransactions and lootboxes that I can avoid paying for, and get the more meaningful content for free, instead of paying for the privilege of getting more content that nobody plays - though this is multiplayer only.
As for lootboxes vs microtransactions. Frankly, I think I prefer the boxes, because they can usually be earned for free, in-game. It all comes down to the drop rates, though. Something like Overwatch is just too slow, but HotS hits the nail on the head.
So long as the boxes are cosmetic only, I don't really mind them, but they are the lesser of two other evils.
Conclusion Part 2 - That being said, I do still believe that adding in F2P payment models into AAA games is insulting and greedy. And can we just shine a torch onto games like Shadow of War that double-dip with both lootboxes and season passes? I mean please.