I too have been frustrated in the past, so I've spent 3 years building my own software.
I gave up on Python, its way too slow for my personal requirements. Instead I've written my platform from scratch in Golang. I utilise a web based UI, I use Bulma as my CSS component library and Highcharts for visualisation. I use a Golang based object database (Pudge) for persistence. I use IQFeed and IB as a datasource and IB and IG Index for execution. I've built my own custom data collection, backtesting, risk management, execution, monitoring from scratch.
I download and analyse 1000's of assets, which I then form into portfolios for trading. No open source, or even paid application comes anywhere close to my requirements.
I believe that if you're serious about quantitive trading you need to build your own software. Trading via a generic platform and via charts is not for me.