The Malbim seems to suggest that this represented a turning point in the development of construction and the like, in that the land was now regarded as being fit to support bricks to build on, which would in turn, allow them to keep building upwards:
ויאמרו. תחלה התחילו החדשות בבנות להם בתי חומה, תחת שעד עתה היו יושבי אהלים, ונזדמן להם אדמה ראויה ללבנים וגם לחומר אל הבנין, שבזה יעלו אצלם הבנינים בקל ובמעט עמל, וכבר היה זה נגד הרצון האלהי שרצה שבני אדם ימלאו את הארץ...
And they said - Initially they began their new buildings with that of walled houses, as until then, they had only lived in tents, but now there was an opportunity for them, where the land was fit for bricks and also materials for building, in which the buildings would rise with ease and little toil, and this was already against the will of G-d as He wanted humans to fill the earth...
This developmental change is also noted by Radak when he analyses the repetition of "נִלְבְּנָ֣ה לְבֵנִ֔ים":
נלבנה לבנים, תוספת ביאור, כמו (מלכים ב' י"ב) ויצום דוד צום, והדומה להם, וכן נשרפה לשרפה, ובאותו בקעה אין אבן לפיכך כל בנינם בלבנים והלבנים עושים אותם מן הטיט ואחר כן שורפים אותם בכבשן
נלבנה לבנים - the word נלבנה is a form of elaborating on something which had been said before, similar to Samuel II 12:16 "ויצם דוד צום" - “David fasted a fast.” If he fasted, he obviously observed a fast; the author wanted to lend extra emphasis to his words. So here too, the words "נלבנה לבנים", though an obvious part of building a city, were repeated merely for emphasis. The words נשרפה לשרפה, inform us that the valley lacked stones for building houses, but that there was clay which could be kiln burned and produce rain proof bricks, making it possible to build permanent homes.