Question

Why wasn’t the style of Roman temples suitable for Christian worship

Answer 1

One reason on why the style of Roman temples aren't suitable for Christians is because they're not built like churches, churches have an enormous amount of space and they're made so that people can stay indoors. Whereas, in Roman temples most activities are held outdoors.

Answer 2

The Roman temples were not like churches, which accommodated large crowds indoors to attend mass or service. The templum (temple) was a sacred precinct, a space for rituals,and much of it was an outdoors. space. The actual building of a temple or shrine was called aedes. Religious ceremonies included a procession and sacrifices which were performed outdoors. The main room of the aedes (the cellla) had the cult image of the deity to whom the temple was dedicated and a small altar. The altar was used for the offerings of incense and libation (liquid offering) which were part of the praefatio, the introductory rite to an animal sacrifice.
The Christians needed to accommodate large crowds to attend mass. Therefore, they modelled their churches on the Roman basilica, which was a public building which housed the courts and other public facilitates, because it could host large crowds.