Its not a new technology I was playing with and extruded ABS one at uni 15 years ago to make prototypes and visualization models and TBH that’s primarily what they are still used for.
For the most part it’s still far too expensive and limited to replace injection moulding in most consumer products.
TBH “printed products” are a nice idea but some way off of being generally viable.
If you fancy building your own Google “reprap” and have a poke about on the sites that turns up, realistically you can make a small rapityper for about £350-£500ish but in some ways a CNC router is a more useful tool to build…