I'm not sure the file limitations are much of a factor when 100mb covers most files that would need to be sent through a messaging service. There are plenty of dedicated services for sharing larger files.
I mentioned it because it was an annoying limitation for me. 100mb is not a lot for media and zip files nowadays. And I don't know any good free services that will work more conveniently than simply sending with Telegram, suggestions welcome.
https://toffeeshare.com/ is what I usually use for big files. But both sender and receiver need to be online for the whole transfer. It doesn't store anything you send on their servers, but that's a feature for me ¯\_(ツ)_/¯
As long as your messages are end-to-end encrypted, I don't know why you would care about that. It's proven that they do not collect any metadata that could harm your privacy and most of their stuff is open source. The signal protocol is a pretty solid protocol supporting E2EE. There are not even cloud backup options, so your messages can never be read from someone other than you and the receiver, unlike something like iMessage that has cloud backup option that backups your messages stored locally on your device probably in plain text to iCloud.
I've been using Signal for a long time now, it was great until they ended SMS text support, then they started trying to turn Signal into a social media thing, I just want end to end encryption without having to worry about somebody like Zuckerberg having access to my texts.
I agree that signal is superior in terms of privacy but a lot of people don't care about that. And most people using WhatsApp DEFINITELY don't care about that.