Verify Google Account Without Old Phone
In order to stop people from creating spam accounts that are solely used to send unsolicited emails all over the world, Google requires a phone number. They restrict how many accounts you may link to one number.
An account that has been reported as a spammer is blacklisted, meaning that emails from it are not accepted as often or at all. The sender needs to register for a new account or show over time that they are only sending emails that others want to receive.
For a spammer this creates a lot of work.
For the rest of us, that’s a good thing.
Google profits on accounts that people use regularly, not accounts that are used to send hundreds of emails with little content viewed. Since Google loses money when we stop using their mail system, it doesn't really matter if you're upset by spam. In any case, we small people benefit from their efforts to combat spam.
You can turn off 2FA in your settings if you want to access Gmail without requiring an SMS confirmation, but you should really leave it enabled.