Is it crazy to be in Paris for Bastille Day? Is it better to arrive and leave before it or after it?
We didn't find it to be as crowded as major parade days in New York City. But as "tourists" (I mean that as a neutral, identifying term ... ) you might find that having many museums and restaurants closed to be a "waste" of a precious day of vacation. Can your hotel charge different prices for different days? We enjoyed the parade, although the sidewalks are crowded. And we had a hotel with a view of the fireworks, although there are plenty of public places besides the Champs de Mars where you could stand.
I would say it's not necessary until your fourth or later trip to Paris. It's unimportant whether you vacation before or after it. Just watch for European vacation month of August. I now consider air conditioning essential for European summers. Street noise and lack of window screens are specific issues, as well as heat and humidity.
Museums don't close on Bastille Day -- in fact when we were there, the Louvre was free that day and not crowded. As my husband noted 'the tourists don't know it's free and the locals have better things to do.' Paris is a huge city; except for the parade on the Champs Elysees and the fireworks you will hardly notice anything different. The night before the fire fights in the arrondissements have 'balls' and some of them are quite informal and tourists can join in. We danced in the street in the 20th to a small band.
We didn't have any problem finding places to eat either. This is a non-issue.