There are various accents in French-speaking Switzerland as well as French-speaking Belgium and I assume local speakers can generally recognise them, but in general French just diverges much less than German (or Dutch to talk about what I know better) and within Europe, French accents are quite light.

It might be due to the strongly centralised languages policies of France and the weight of France relative to the rest of French-speaking countries, I don't know, but basically the only accents that can actually be a bit complicated to understand are those of Québec and Louisiana, which have spent several centuries with basically no communication with France.

There's also Africa but I can't speak about the varieties within Africa though, other than the obvious accent difference between North Africa and Sub-Saharan Africa.

What about Marseilles?

It's "strong" relative to French regional accents, but easily understandable by any French speaker around the world, without special efforts needed. It's not really comparable to Swiss German accents.

French people typically don't figure out the different swiss french accents and label them as one "swiss accent" but having lived 18 years in the french speaking part of Switzerland I can assure you there are enough differences between accents to figure out from which canton, or even cities sometimes, people are from.

I mean, most Swiss French accents share common characteristics (e.g. stress on the penultimate syllable and descending intonation on the last) but having grown up near the Swiss border people there really differentiate the Genevois, Vaud, Valais accents, etc

It's not the same scale as Swiss German accents that are sometimes completely unintelligible for German speakers, but I have to admit there have been a few times I've been unable to fully understand someone speaking a thick Swiss French accent