It's been a minute since I've actually looked at Basecamp, Maxime, but last time I did, its tasks (To-dos?) were flat (no subtasks, etc) and lacked dependency linking. It only supported Kanban processes, which are good for bug fixing but beyond useless for iterative sprint planning and tracking.

My world, at least, is a lot more complex than Basecamp's very basic model was prepared to take on last time I saw it.

Far superior document sharing and collaboration can be had for free from GSuite, and much better messaging is available from Slack.