If you work alone, your calendar and todo lists are what you put there with you as the only editor. So whether, you use pen & paper, a spreadsheet, a text file in Google Drive, or whatever, does not matter to anyone except you. So, whatever works for you. I'm a pen & paper guy. But as soon as you are not working alone, you need different tools. Mostly, my pen & paper work eventually ends up in a proper tool.

Any time slot that matters to me goes into a proper calendar so my time is marked as blocked and people know that I'm busy and don't dump meetings in it. I literally block time to code. Likewise, a lot of my work is coordinating work with others and we use Asana and Github issues for that sort of thing. Other tools are available. But the key feature usually is that you can use them with a team and assign stuff to each other, edit them concurrently, and have some non technical team members doing so as well.

Doing csv exports and imports is feasible for calendars and issue trackers but it doesn't solve a problem I have (except when migrating to different tools). As data input tool that seems not really great. It's actually why I like Asana; I can just type an issue, hit enter, type another one, etc. It feels like a spread sheet tool.