You can definitely use Telegram instead of using social networks (I know that because I do that as well). However, that doesn't make Telegram a social network by definition (I know that because I used to run a social network).

Social networks have features like friends lists (which are public by default) or user IDs used to log in (separate from mobile phone numbers). Pretty much all of them have algorithmic newsfeeds and two-level comments (except Twitter). The largest social networks in the world are Facebook, Instagram, TikTok and YouTube. We at Telegram don't want to become like them - we like being a messaging app 🙃