What they're complaining about is a lack of "slack" to take on un-prioritized, but important work.
Slack is important for any healthy team.
How?
Give them time to work on those improvements.
Let people fix high-risk issues; before they are a roadmap disrupting emergencies.
Give them time to test their guesses; they will construct load tests, and figure out projects for the roadmap instead of waiting for emergencies.
Empower natural creativity.
Large projects like AWS migration, or re-arch. for long term growth are a different beast. They're eng-driven roadmap items; which also need to exist, but often don't get prio.