Hi Velson,
Unfortunately, unless you write and maintain your own software, there will always be changes that you don't expect and even don't like. However, if you don't have that capability, there are ways to manage the changes to limit any negative impact, e.g.
- Check the release notes before upgrading.
- Choose your upgrades carefully - you probably don't want to upgrade to the latest version, as that means a major update every six months.
- Test the new version before upgrading your production site(s) - maybe there are some things that you won't find until real-world use, but reading the release notes and some testing should protect you from most surprises.
- Plan for upgrades - make sure there's enough time to do the above before the version you're on falls out of security support.
If you're not in control of the upgrades, you need to get the people who are to do those things, and communicate/coordinate with you about it.
I'll also note that the developers definitely think about the consequences of changes, and it's unfair on the developers to say otherwise. They are however humans like the rest of us, so can't envisage every possible way that Moodle may be being used. They try to incorporate existing sites, and ease upgrades - e.g. the assignment upgrade tool. Additionally, the Moodle development process is one of the more rigourous that I've seen around the open source world.
Although Moodle's rapid pace of change can be hard to keep up with, I think it's pretty amazing that all this functionality is available libre and gratis - and is continually added to and improved upon.