Check internal dependencies only before activation

[btry]

in some cases, it may be impossible to clean, install or upgrade the plugin becausee of prerequisite checks.

[AdrienClairembault]

Isn't it risky to allow installing the plugin without dependencies ? Some upgrade code might use vendors code.

Not mandatory but if you want you can also use $plugin->isInstalled('formcreator') && !$plugin->isActivated('formcreator') as an alternative condition.