If you want a big app, with a lot of functionalities, exploring data from many different angles, used by a lot of people etc - go for Shiny(if you are using R) or Dash(if you are using Python). You can easily put Dash in Flask or even Django if you want to build even more advanced web apps.
BTW depending on what you try to build, dash might be significant slower/faster in development time comparing to Power BI or Tableau.