No. A Tirthankar is not more negligent than a muni or a good śrāvaka.

In Jain Dharma:

• Tirthankar is the highest spiritual being in the world system after omniscience is attained.
• A muni is a renunciant who follows strict vows and discipline.
• A good śrāvaka is a lay follower who practices Jain dharma sincerely with restraint.

In terms of pramāda (negligence):

• A Tirthankar as an Arihant/Kevalī is completely free from pramāda.
• A muni has very high vigilance, but until kevaljñān there can still be some subtle limitation.
• A good śrāvaka also practices restraint, but in general has more worldly involvement than a muni.

So the correct understanding is:

A Tirthankar is supreme in spiritual purity and is not negligent. The order of vigilance is generally: Tirthankar/Kevalī > muni > good śrāvaka

If you want, I can also explain the difference between pramāda, apramāda, and vigilance in Jain ethics.