If you board the 69 near the Eiffel Tower or at Gambetta this can work -- because you can probably get a seat and the bus does go through many well known parts of Paris including through the Louvre, around Bastille etc. If you grab it midway somewhere, odds are you will be standing and not seeing much of anything.
To clarify the earlier statement on ticket use. You do not have 90 minutes of bus time; you have one ride. You can do a transfer if needed to get to your destination and that is one ride. But you cannot board the same bus during the 90 minute period.
We used to use the Strippenkart in Amsterdam and you could use it there for a time period. In Chicago you can use bus and El charges with a very small transfer fee within the time frame; I often run an errand and return on the same punch. But in Paris this is not so -- it is not a timed ticket; it is a one trip ticket.