I personally am not. But we as a society typically come to a consensus as to what is rude and what is not.
This very thread proves this point.
This is entirely separate from my opinion on whether the situation described in the OP is rude - but you feel like yelling INSIDE VOICE at people who are outside? 
Every time I go to the doctor, without fail, there are older folks (65+) having phone conversations while we’re in the waiting room together. I feel embarrassed for them.
The grocery store is also full of people talking on their phones. It makes me anxious.
Then again, I remember being on the bus in college in the late 90s and my peers were talking on their phones too. That might be different because people are expected to be inconsiderate on a bus 
It happens everywhere, hospitals are no different I guess.
Sometimes, one family is overjoyed at the birth of a new member of their family, while another family just lost a beloved member of theirs.
And they often sit in very close proximity in the same waiting room/area.
So they really are not all there for the same reason.
That’s part of what I mean when I mention being sensitive to the possible circumstance of others waiting in/near a hospital.
All I can say is that I have spent a lot of time in hospitals, and other people’s conversations were the least of my concern. In fact, I found people with happy results comforting. The time I was checking my mother (dying from congestive heart failure) into the emergency room directly in front of me in line was a woman in labor. Should I have been offended that she was there for a good reason and I was there for a bad one?
Because a person using an electrolarynx doesn’t have any other options, so he gets a pass, kinda like a person in a wheelchair gets a pass when everyone else is supposed to stand (anthem, judge entering courtroom, etc.). Likewise, a person with Tourette syndrome who can’t control their tics should be allowed to check out a book from the public library without being given a hard time; that doesn’t mean people without TS should be allowed to make random loud noises in the library.
The people who ought to be in your class are the self-absorbed nitwits who insist on loud phone conversations in quiet, shared public spaces, seemingly unaware of the people around them. It’s not a matter of who’s worthy to have conversations, it’s a question of consideration with regard when, where, and (especially) how. If you firmly believe that no such consideration ever need be given, then I’d invite you to try having a speakerphone conversation while attending the changing of the guard at the Tomb of the Unknown Soldier.
I was hoping it would be a way to actually crash their phone remotely. That would be wrong. But oh so satisfying.
Where, exactly, did the OP say that the conversations are loud?
I remember the time when people were saying cell phone calls were more annoying than “everybody present” conversations because you only heard one side of it. Now it is annoying when you hear both sides, too?
Sorry, but it all sounds like “old man yells at cloud” to me. (And I don’t even use my cell phone for voice calls.)
I really think that was implied, but yes, for posterity, they WERE loud.
ETA: also this from my OP:
So it was not only implied, but spoken out clearly.
Yeah it’s rude.
When both people are present for a conversation they are typically aware of their surroundings and will speak at an appropriate volume and stick to appropriate topics. When the person on the other end is coming through on the speakers it’s often quite loud, it sounds obnoxious because of the speaker quality, and sometimes they talk about things that are extremely personal or just inappropriate for a public venue.
You’re angry that you can hear people through your open window?
They are across the street, by themselves. There is no need for shouting at their phone at levels I can hear 20-30 yards away.
I just don’t know why you think that. If playing everything out loud was the norm, there’d be no reason for earphones (wired or Bluetooth). Clearly there’s some expectation that you keep the sounds of your phone to yourself, just like there has been for other portable sound-making devices.
I’ve even been around when one person ignores this etiquette, at a doctor’s office no less. They were either listening to a video or had a game with sound on, and everyone around was sideeying them. I actually looked to see if they had an earpiece, so I could tell them that it hadn’t paired properly with their phone. It was awkward.
I’ve found I have to use speakerphone, or an earpiece, to hear anything on a cell phone. If I leave the earpiece attached I will not hear the phone ringing, so at least the first minute of an incoming phone conversation has to be held on speakerphone.
Also, if everybody in a radius of 20 meters has their phone on speakers, everything becomes a cacaphony.
I think it’s very rude.
There’s this guy at the gym that seems to take all of his work calls while he’s on the treadmill. Our workouts have overlapped on a number of occasions and I find it EXTREMELY irritating, probably way out of proportion to how much of an inconvenience it actually is.
Is it annoying? I guess so. I just tune it out. It was particularly distracting at first, now I’ve just decided to learn to live with it and just filter it out. Now that I don’t pay attention for it, it doesn’t bug me.
It’s kind of annoying when someone’s talking on their phone in a waiting room, but I can’t help thinking that everybody in that room now knows a bit of this guy’s private life. Serves him right. 
I’m not yet at this point that I can filter it out. Maybe I have to become accustomed to this fact of life, but right now it still annoys me.