Archibald Tarquin Blenkinsopp Esq expressed precisely :
Diagnostic abilities?

The ability to diagnose part xxyyzz being defective and finding that
the part is obsolete or costs nearly as much as the original boiler?

Much like vehicles too, but would you want a vehicle these days as
basic as an Austin 7?

Our new Vailant can inteligently decide just how much heat it needs to
produce to meet its desired room temperatures, taking into
consideration the outdoor temperature and indoor. It doesn't overshoot,
rather it learns what is needed and can modulate right down to match
the demand. The pipes don't creak and moan anymore.

The previous boiler either ran and produced full heat, or none, though
it did modulate, it only modulated based on its internal temperature.