Congregational prayer, even if it includes sermon and teaching, is not for the demonstration of the genius of imam or his great devotion to Allah. Admonition, sermon, teaching, passing on information have to be followed by such a long prayer that everyone can easily perform.
Caliph Al-Mutawakkil reigned from 847-861 in Baghdad. Attached to him is the case of someone slapping an imam. He was immediately taken before the caliph to do justice. Al-Mutawakkil questioned the perpetrator about the motive of his act. That's what he told. One day I went on a hard journey into the desert and I returned late. I had just arrived at the time of the Fajr prayer and thought before going home I'd better if I fulfill my duty towards Allah. I entered the mosque where the imam just lined up the believers and started. Being two Raka’at prayers, I thought I can get over it soon. I could barely stand on my feet from the fatigue. The imam in the first Raka’at began to recite the Surah of Baqara (the longest Surah in the Quran) and he passed through it accurately. When we reached to the second Raka’at, I reassured myself that the Surah of Ikhlas, or a similar very short verse would follow. And the imam started to recite the Surah Al-Imran (this is also long). By the time he went through, it was about sunset. We were just about to say salam when he got to his head. Allah forgive my sin, he said, I was not making ablution before prayer, it all has to start again! That's when I slapped him. All what Al-Mutawakkil said about it was that he would have slapped him too. Then the man left freely. This story was told by Sheikh Dr. Omar Abdel Kafi (may Allah be pleased with him).
The story is good for highlighting the importance of sensitivity towards others. It’s not always just me who needs to be considered, but vice versa. I have to be considerate to others, too. People come to congregational prayer to hear admonition, teaching, to fulfill their duty towards Allah, then they leave in order to do their business. The role of imam is important in establishing this situation. If he doesn’t do like that, he doesn't know his role. It is not according to me, but according to the Prophet (peace be upon him):

Abu Mas’ud reported: A man said, “O Messenger of Allah, I am late to prayer today because such a person makes it too long for us.” I never saw the Messenger of Allah, peace and blessings be upon him, as angry in his preaching as he was on that day. The Prophet said, “Verily, some of you cause people to flee. Whenever you lead people in prayer, then lighten it as among them are the weak, the elderly, and the needy.”
Source: Ṣaḥīḥ al-Bukhārī 670
Grade: Sahih (authentic) according to Al-Bukhari

I can continue this call for sensitivity in order to respect the private sphere of others as well. I try not to disturb the privacy of others, not to obtrude into it with indiscretion. At the same time, I often find that we tend to ask each other meaningless questions, send all kinds of documents and attachments online in vain. First of all, we should know if we uphold the other person and weather is he/she interested in our inquiry or document at all? And if you’re both interested, don’t ask "keif al-hal" (how are you?) for half an hour, because it can be damn annoying. Get to the point and tell what you want. When you finished, say salam and go for your business. This is the behavior that must be followed in Islam. That half-hour check-in and health inquiry of all family members, including pets, is not appropriate. Let’s not confuse politeness with empty fuss. We have to respect each other's time and pursuit. I am not speaking now about the talk between family members!

I was writing about the duration of the congregational prayer above. If you perform salat alone, it's different case. Give what you have to give to Allah according to your conscience, but do not forget your family, your daily work and your prescribed obligations. Don’t try to escape from any of them with “devoutness”.