Alternative to Microsoft Planner for managing tasks

Help me get promoted again!

I made a solution for the small company I work for to help the backoffice team to get solicitations from the operations teams.
Basically, I built a simple Teams App, that shows a Sharepoint page with a Forms embedded.

When someone sends an answer in the forms (requesting vacations, for example), it triggers my MS Automate flow to create a new Card in a Planner, setting the the due date, the specific responsible for that issue, etc. The card shows the info provided by the requester, and an e-mail is sent to both, the requester and the responsible for the service. All the data is displayed in a Power BI dashboard for management.

Things turned out to be a hit, and now the whole solution has a proportion that is making MS Planner unsuitable to the job.
For example, people can only close the card, but there is no way to say that request was successfully closed, canceled or any other thing. Also, there is a limit of 3000 cards assingned to a single user.

Is there another tool I can use to replace Planner as the platform to the backoffice teams manage their tasks?
Preferably a tool inside the microsoft 365 Business Standard subscription.

Quick Links

Leaderboard > Power Automate - General Discussion