In fact some "common cold" coronaviruses are really quite similar to SARS-ncov-2. hcov-NL63's protein spike, for example, binds to the same ACE2 receptor, and

In fact some "common cold" coronaviruses are really quite similar to SARS-ncov-2. hcov-NL63's protein spike, for example, binds to the same ACE2 receptor, and is also believed to be a polymorphism of bat and civet coronaviruses. It's also known to cause pneumonia in immunocompromised patients. But of course, a big difference is that hcov-NL63 has probably been circulating in humans for centuries, so we tend to acquire immunity to it by being exposed as children.