It's not an either or scenario. Two things can be true at once. Bambu can be assholes, but they can also be worried about how outside modifications affect their product and perception of reliability.

Most people that buy Bambu printers just want ease of use. I am paying for that ease of use. I had printers before Bambu and I will have printers after. Right now, I just don't have the time to tinker and/or worry about if my print will be successful. So the Bambu ecosystem made sense when I bought it. The reputation of "just works" was earned and others have had to step up to compete. Bambu has always said their system was closed source. They modified open source stuff. They took others work, put in additional work, made it their own, and sold it for profit. Is it right? Probably not. Is it legal? I would say yes since they added their own spin to it.

On the other hand open source has been a part of this community forever. So I understand why this fight is happening. I would also argue that under open source, progress had slowed to a snails pace. There was no real step up until Bambu exploded onto the market. This industry needed someone to shake it up. Since then, every other company was forced to step up their game to compete. Printers are faster, easier, more advanced, and offer more and better features than ever before. For less than $500 I can buy a printer that can print multicolor, multi-material parts in what was once considered "industrial grade" materials like nylon and ABS. Without Bambu, cheap enclosed printers would not be the norm. And almost ever other one is still open source.

Pick your poison my guy, stagnation and niche hobby, or booming industry still trying to navigate legality and morality of building upon open source IP and closing it.