It is not possible to accurately describe the difference between Bitcoin and "altcoins" as a single topic. The code for BCH, for example, is extremely similar having been created by a fork of the same code base. The reputation and perceived value, compared to Bitcoin, are dramatically different. XRP (Ripple) has code which is radically different, and is centralized by a massive 100% initial premine. Somehow their reputation among the corrupt bankers has been growing stronger recently.

SOL and Tron, for example, try to compete with ETH as a platform for creating endless more tokens and you can easily start to see why some people passionately hate all altcoins.