the narrative is that the parliament is unworkable, but i don't see why the socialists in france wouldn't support austerity now, as they have for decades. french voters apparently have short memories and got distracted. it was the neo-liberal policies of the previous socialist government that created this situation in the first place.
macron will likely still retain control over parliament, and there is very little that melanchon can actually do about it. the only workable coalition is the one that macron wants, which is a grand coalition that includes his centrist parties, the republicans and the socialists, which are the old bankers parties, the status quo.
you can argue that this isn't the parliament's mandate, but it actually is. there's nothing illegitimate about what happened, but it negates any messaging from the voters. what mandate did the voters hand to parliament? when leftists voted for the centrist bloc, they voted to maintain the status quo; when the centrists voted for the leftist bloc, they also voted to maintain the status quo. ergo, the message french voters sent was clearly that they did not want social or economic change and that is therefore the parliament's clear mandate.
that might not be the message they intended to send, but it is the message they actually sent. clearly. unambiguously.
i think that macron should resign and that there should be new parliamentary elections, but i don't expect that to happen. rather, i expect a grand coalition to develop out of the old bankers parties - the socialists and the republicans - and for it to implement vicious austerity. the french people got a little uppity here and will need to be punished for it with vicious cuts to social spending. this will in turn merely generate further support for what is being called the far right, but is being strenuously opposed by the status quo because it is actually a real left.
french voters need to learn the lesson, which is to never trust a banker. unfortunately, they're going to have to learn the hard way. worse, they appear to be slow learners.
the other possible outcome is that the parliament is unworkable and a new election is coming soon, but i don't think that the socialists, who won seats, will allow for that outcome. the socialists will work with macron, and that will be enough to hold the government.
i also want to point out that, while exit polls are very reliable, they are essentially a survey of the population, with a margin of error. this particular election will have a lot of very close results. there is a caveat that the projections may be substantively wrong, and if that happens it will not be because the exit polling was wrong but because the error wasn't properly accounted for. if ~40% of the seats are within 3%, as i believe is the case, the exit polling is of limited predictive value. note that this caveat works in both directions.