Short answer: Yes absolutely. Solution: use a file sharing service like Dropbox or Google Drive instead if quality matters for what you’re aiming to do.
Facebook Messenger absolutely does compress the images that you upload. This is simply to save bandwidth when you come back to view the image on the platform and to save on storage space. As you can see above, by compressing the original image over 4MB has been saved in terms of the image size.
The resulting image at 3641x2048px is plenty big enough for most uses, especially if you are viewing the image on a mobile. However, if the image quality matters then you should use a file sharing service instead of Facebook Messenger to share images. For example, if you are sharing images to go on a website then it’s best to share the files through something like Dropbox or Google Drive instead of sharing using a messaging platform.