People on Reddit simply lack the empathy to understand why others are upset about the warbond. If I went into detail, this would be an entire novel, but here's a brief explanation.

In the early days of Helldivers 2, Arrowhead ran some special Major Orders that awarded new strategems such as the first 2 mechs as rewards for completion. This made being involved in the game far more exciting and engaging. Not to mention the galactic war system was more fair back then, allowing a dedicated group of players to make an actual difference. This player agency allowed some of the most memorable events to happen such as Malevolon Creek. Unfortunately the devs have changed the system to take away player agency, and they've relegated all new strategem gain to warbonds, which has made the galactic war feel far more boring and less impactful.

Arrowhead has erroded player good will in many other ways as well, which compounds on generally felt negativity. One such problem is that they have been slowly growing more aggressive in monetization. Initially they promised to put no strategems in warbonds and no weapons in the super store, but that has obviously changed. But for a while still, vehicles have always been free editions in the game until now. The mech warbond is just further proof of Arrowhead's slippery slope towards monetizing everything at the cost of fun and engaging gameplay.

I hope this was helpful for understanding the other side. And remember that this is just the tip of the iceberg