The following winter passed without disturbance, and was employed in salutary measures. For, to accustom to rest and repose through the charms of luxury a population scattered and barbarous and therefore inclined to war, Agricola gave private encouragement and public aid to the building of temples, courts of justice and dwelling-houses, praising the energetic, and reproving the indolent. Thus an honourable rivalry took the place of compulsion. He likewise provided a liberal education for the sons of the chiefs, and showed such a preference for the natural powers of the Britons over the industry of the Gauls that they who lately disdained the tongue of Rome now coveted its eloquence. Hence, too, a liking sprang up for our style of dress, and the “toga” became fashionable. Step by step they were led to things which dispose to vice, the lounge, the bath, the elegant banquet. All this in their ignorance they called civilisation, when it was but a part of their servitude. Tacitus - Agricola 21
In this passage, is Tacitus essentially saying that Rome's investments in Britain (ex: construction of courts, houses, temples, baths, etc.) were intended to condition Britons to accept Rome's rulership over them more easily?
The passage certainly is talking about how Rome, especially in western territories, would follow a 'format' of buildings to be constructed within Roman settlements as method of creating continuity throughout the Roman territory. The bolded part of your quotation however is Tacitus echoing similar ideas from past writers regarding the link between luxury and decadence, as well as how the introduction of luxury can lead to subservient behaviour.
There are plenty of examples from Polybius to Livy that suggest links between the introduction of luxury and moral decline and the topic itself is incredibly complex, but to try and answer your question there is a passage in Sallust (War with Catiline. 10-13 esp.) which provides a similar idea seen within your passage:
Besides all this, Lucius Sulla, in order to secure the loyalty of the army which he led into Asia, had allowed it a luxury and license foreign to the manners of our forefathers; and in the intervals of leisure those charming and voluptuous lands had easily demoralized the warlike spirit of his soldiers. (Sallust. War with Catiline. 11.5)
Here, you see the argument that the introduction of luxury was done in order to make the soldiers more subservient to the command of Sulla. Likewise, the introduction of 'luxurious' activities within Roman Britain would be expected lead the further subservient behaviour of the people.
As mentioned previously, the concept of the links between luxury and decadence is incredibly complex with various nuances (is what was written by the authors true? Was it political rhetoric? Did other factors play a part?) but that is what makes it so interesting.