I know exactly how you feel man. It is a sad reality of this game now that all the time and/or money you invest in your mechs can be flushed down the toilet whenever the developers feel like. This kind of laissez faire attitude is not only disheartening but very unethical as well.
Considering that building a competitive mech is so much more expensive in this meta, both in terms of time and money, I find it very irresponsible for the developers to issue game-changing updates with no regard to the players that have worked so hard to get where they are. In the previous version one could try and adapt to these changes by fusing a redundant item into an alternative one. The fact that fully fused items retain less than 10% of what it cost to fully fuse them is infuriating and adds insult to injury.
The developers keep changing things on a weekly basis, while players are still expected to pay extortionate prices or grind the game for even more ridiculous amounts of time to keep up is highly abusive. I voiced this sentiment when the update rolled out, when i fused all my legacy items and committed to the new game I (and so many others) predicted that this scenario would happen - and unfortunately it has. It makes me wonder how much longer this will continue and if we're seeing the beginning of the end so to speak for this game.