Is it worth upgrading Macbook mid 2010
In the corner of the world where I live there are still plenty of MacBooks Pro 2010 in circulation. But you have already done the main upgrade that I do for my clients: swapped the spinning HD with an SSD.

I get the impression that you really want there to be a path to a good upgrade. But the reality is as you say that it has a C2D CPU which just doesn't cut it anymore.

Also it can only run macOS 10.13.6 max, so software wise it will always be stuck in 2017, and apps and upgrades will slowly leave it in the dust.

I do not personally think it is wort spending much more money on. But, it has a SSD and therefore it should run reasonably ok as it is. Its 6GB of RAM isn't hopelessly little, especially not if you keep at least 20GB free on the SSD so it can swap nicely (it's an SSD, so the swapping will be quite snappy). 

Its loud fans do not jive with my experience of everyday use though. Why don't you, if you want to give it another look, try to address just that. I would do two things:


Reinstall it cleanly with macOS 10.13.6, making sure you leave any old OS cruft out of the installation. Note that if it currenlty has a
very old version of macOS, you might have to two-step it through
  10.11, as it is sometimes impossible to upgrade direclty to 10.13. Also note that you might have to backdate the Mac's clock a few years
while the installation is ongoing to allow it. 
Open it, check for dust in the fan duct and remove and reapply the thermal grease between CPU and heat sink.


And then in use, make sure you keep at least 20GB free on the SSD so you keep macOS happy and non space-constrained