The best replacement for sandbox is theme park.

The best alternatives to sandbox are rated as following:
★★★★★  theme park
★★★★★  sand table
★★★★  open world
★★★  virtual machine
★★  farm solution
★★  survival project zomboid
★★  vm
★  all-permissions
★  sandboxie
★  themepark
★  sandpit
★  rockbox
  bern
  water and sand table
  free roam
  foundry
  live paypal
  sand box
  dfx

Your alternative for sandbox is not listed? Suggest!
Speaking about sandbox, one probably shouldn't forget about picnic table.

Other search terms related to sandbox and their ratings are:
★★★★★ picnic table
★★ slide
You have in mind a companion for sandbox and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of sandbox in all years. Click on graph for more.
sandbox
theme park
sand table