Mercurysteam making the game online only was one of the reasons I walked away from it a few months ago. I may be playing Raiders/Broken Planet again, but the move to online only was shady, and I wont spend another dollar on anything Mercurysteam touches again. Hopefully one day they make the game online/offline again.
What..is shady about being online only? Some of the most popular games in the world are online only. Just off the top of my head; World of Warcraft, Fortnite Battle Royale, League of Legends, Defense of the Ancients, Spacelords, Counter Strike: Global Offensive and etc.
That stuff.
I stuck around. The point is that if people had the option to grind offline then it introduces massive balance issues, not to mention a more easy avenue through which to hack the game. How would rewards work for offline? Would you get the same amount of stuff as your online counterpart? Then the challenge would have to be similar and good luck soloing Short-Fused and scoring really well when you're the only thing the AI will focus.
But beyond that it is the intention of the developers to present their game at its fullest the very first time it is played. I'm sure there are many stories of impossible scenarios given to a group of Raiders, like they are all low level and they must contend with a high level Antagonist, and I have one too. Just less than 5 matches in I ran into a very high level Antagonist and I was absolutely shredded. I really had no idea what was going on and I appreciated the game's brutal nature. But here is the thing I had won my last few matches which only contained the AI. When I was first invaded my thought was "Dark Souls with guns" and I loved it. I still do.
There are many factors which are involved in this discussion. Especially since it is, like usual, becoming a thread about Antagonists. Which makes sense; the Antagonist feature is a very good one and without it this game would be less. So it is important for you to understand this thing.
Competitiveness breeds innovation. It makes things interesting. Once you have done the 17 missions 40-50 times each you start to wonder what other challenge there could be. I know that I instinctively know where things will spawn, how long it takes to do such and such action etc. But an Antagonist switches it all up.
It makes it fun. If it were playable offline and online then those people whom do not like Antagonists would play strictly offline. And, logically, I wonder what they are playing a game that has Antagonists for in the first place? There are many other games which do not have such systems of PvP.
So, I think it is more a matter of wanting to win at something without a challenge in place. Because Antagonists are a major part of the game and not liking them is almost tantamount to just not liking the whole game, can you truly say you like the gameplay if you hate 50% of it?
It is not wrong for the developers to choose how they want to present their game, it is their investment, their work, their game.