Before talking about architecture decisions, it helps to have a shared mental model of what cloud computing actually is. This explainer from Google Cloud is one of the clearest plain-language overviews available.
The framing around elasticity is correct in principle but understates operational complexity. Infinite scale does not come free — you trade capital expenditure for operational complexity, and the crossover point varies significantly by workload type and team maturity.
The best cloud migrations I have been part of started with a clear-eyed audit of what was running on-premise and why. The worst started with a mandate.