Todoist has stuck with me for years.
The key things that made me switch (and then) stick:
- Recurring dates - agree with @bowline, the recurring date handling is excellent. The two options for recurring (recur based on due date, or recur based on date completed) were a game changing improvement on my previous tool. Good automation.
- Shared projects - I’m not interested in a system that can’t do this. I have projects that are just me (eg. work, personal), but I also have projects with my partner (eg. house chores). I don’t want to look in different systems for the things I have to get done.
- Filters - the custom filters do a great job of helping me focus on my current context.
- Automation - I’ve been adding certain tasks via IFTT/Zapier for years. It’s excellent.
For me personally, the subscription price is a bargain for what I get out of it.