Why is my MacBook Pro headphone output so low?

You were right. I found my mistake. Even though the satellite speakers are away from me and in the back from the laptop, somehow, the volume adjustment on the right satellite had been lowered without me realizing it.

I'm good now! Thanks for reminding me about the volume adjustment!

No, I didn't try another brand. Before the last major update to Sequoia, the SoundStick was very loud at full power. I have no doubt that it's working fine but, like I mentioned, I got another SoundStick and got the same results, very low output. I switched the cable that connects from the SoundStick to the Mac but it didn't improve anything. I don't have any other equipment that I could test, unfortunately. But, like I said, before the last update to Sequoia, I would not run the volume at full power because it was too loud. Now, the volume is at the maximum but I can barely hear anything. Something is wrong somewhere with my Mac or the system...

I will try to find a headphones that I can connect to my Mac. I don't have one right now.