I’ve been using MLO since 2015, so I know exactly what you’re talking about.
I have switched this year to doing my GTD inside Obsidian with the help of a custom-built script designed to replicate my most-used GTD functionality from MLO. I’ve created a guide and demo vault here which you can check out:
There is almost certainly functionality you need from MLO which is not covered here. While it’s definitely harder to achieve what you want in Obsidian, I now believe that it’s possible to replicate almost anything from MLO inside Obsidian with a bit of scripting.
As a side note, I don’t use reminders in my Obsidian task list. Per my understanding and practice of GTD, anything that’s date-activated should be in your calendar.