Elections are not, and should not, be the be-all end-all of a functionning democraty. Otherwise you just have an elective aristocracy.
And to be clear, I'm not saying pure polling driven policy is the solution, but saying politician should outright ignore them because not legally binding is a very weird stance.
If anything, the origin of the 5th republic under its founding president used referendums to validate the president's actions. He literally resigned after losing a referendum https://en.wikipedia.org/wiki/Charles_de_Gaulle#Retirement.
The only polls that matter are elections. Apart from elections, people have the right to avoid any poll without risking any policy change.