This is always the case. It is always OR never AND.
There are talks about how technology is the key to a successful product. May be it is true in the beginning, till one has to maintain it. Almost all successful products in the market are not of the latest technolgy. There are some parts of it is new technology, but majority is old, very old. The technology they use are once new, but now it is old and that is ok. No one cares what the technology it uses behind the scenes. As long as it solves the purpose, it is fine.
Once you focus on a product, there bound to be a Technology lag. However if you focus on technology there bound to be a product lag, in terms of UX, UI, Feature, Marketing, Sells or a combination of all these.
Even making a small Javascript library is also a product. And that also walks this path.
Important thing is, what is your focus. If technology is the focus, product will be perpetually be half-finished. It is not that product will be unfinished, but half finished.
Make a library, let it solve the problem in hand.
Use the product to make new products which solve problems. Use technology to iterate the product, but let the focus be in the product.