Just checked to see if my jar of Marmite is still in the cupboard - it is. It's also probably still good with the amount of salt in it.
I think my issue with the product is its use is completely at odds with the actual flavour. The other closest thing I've eaten would be that Better Than Bouillon goop:
Which is meant to be diluted in water and used as broth. On its own, it's way too strong and way too salty. That's not to say you could save Marmite by doing that, as it would probably be awful. Stuff really does taste like a dirty cornhole, or that yeast sludge you get at the bottom of your fermentor when making beer - just with an equal volume of salt added to it.