According to the bottom of this CoinTelegraph article:
The Jaxx team clarified that they halted work on Monero due to recent
protocol changes that caused difficulties, and because the integration
had gone significantly over time and budget, and was therefore
hindering development for the 1.2 release.
There was a large divide in the community, and I speculate that Jaxx did not fully understand how to work with Monero. The protocol change they are likely referring to is RingCT, which they probably did not understand the large impact the change would have when they first began development. If you are interested in an approach for a project, c789 listed several resources in their post. Furthermore, I would suggest asking technical questions in the Monero StackExchange, community consenss questions in Reddit, and developer help in the #monero-dev IRC. While people will not write code for you, they can point you in the right direction.