What have I done? A seemingly useless rug.

Rugs used to be put over the washing line and beaten! Good exercise for you?

It's the same with 'dry clean only' clothes and curtains - they tend to be just fine put in a 'delicates' wash.

Two fairly easy-care fibres I would have thought . Probably easier to clean than you think. The cleaning instructions are possibly overcautious.

I would enjoy it, when in dire need of a clean, I would attempt to clean it as others have said it probably will be fine.
The manufacturer add that to cover themselves,I reckon.

The rugs here are spot cleaned, sometimes sprinkled with bicarbonate of soda (to remove any doggy smells) and, when grimy, washed.

Short pile is fine, done with the carpet washer - but long pile rugs are soaked with shampoo (outside) then hosed down. I put them over a wall to do that and they drip dry.

I'll only throw them away if they still look grimy. Oddly, anything left out on the drive is taken away by someone - even a threadbare hall runner and a broken chair.

Viscose and acrylic are eminently washable. Scrubbable even. You could even power wash it in your garden if you have a garden.

If you love it, just use it, enjoy it and chuck it out when it needs cleaning. Life to too short to worry about the future. If you hate it, sell it on!

Will it be somewhere which gets constant tread?
It may not get too dirty, you could try spot cleaning and see how that works if something spills on it.

If someone walked over it with mud on their shoes 😲 the advice is to let it dry first then vacuum.
And banish them to the kitchen.

How about using it as a throw across the foot of a bed?

Can it be vacuumed? Could you clean it yourself if necessary? There are good products available. Don't panic. Put it down and see if you like it. That's what matters.

I'm another whose first thought was a wall hanging!

Sell it on to someone else?

I agree if it's decorative enough it could be a wall hanging - very trendy now.

If it is decorative enough, hang it on the wall or use it as a throw on the back of a sofa - where it is less likely to get dirty enough to need expensive cleaning.