> So while it looked promising, sadly the next day I was already back to using gmail addresses

I know this pain point well. Some sites, instead of using a blacklist of every single disposable e-mail service, just use a whitelist of 'popular' email domains like gmail.com, outlook.com, yahoo.com etc

This is why I have accounts with gmail and other popular e-mail providers. That's the only reason. Sad that you have to conform to be a normie just to use a website. Thank all the bots and bad faith actors for that...