The default processing is fairly aggressive about noise reduction, yes. Here's a comparison on the 12 Pro Max. You can see that e.g. the brickwork and the clock face are clearer in the raw file. Many photography nerds would probably be perfectly happy with the (low) level of noise in the unprocessed RAW shot, but perhaps regular people's preferences differ in this regard.

The original images:

https://drive.google.com/drive/folders/1-2NQ0meQ-PgNvgObWmPT...

A cropped comparison saved as a high quality JPEG, for easier viewing:

https://drive.google.com/file/d/1VEMVPGDE7ck-0du9QYxydM1a3P8...

I don't think the compression is the issue here, by the way. It's just that when you don't shoot RAW you are getting the default denoising+sharpening.