Downloading detailed Investment transactions

Maybe Im misunderstanding your question or request, but I think you might be misunderstanding Quicken's capabilities and functionality. It is definitely possible to record buys, sells, dividend payments and reinvestments, etc. in your investment accounts:

Enabling this is done in the setting for each investment account, by selecting to track investments at a detailed rather than simple level:

If you want, you can manually enter all these transactions. But as you note, most people want to download them to save the time of manually entering them. Quicken supports this, but the question is whether your financial institution does. Some financial institutions may offer only simple tracking of positions and balances, but the vast majority allow you to download detailed transactions. So there's actually nothing Quicken needs to develop here; you just need to select Detailed Investment Tracking for your investment accounts, and verify that they do indeed provide transaction downloads.