Yes — the legacy 2.0 engine is safe to disable on modern Windows, and you can check what might depend on it first.

1. Check the feature state

Get-WindowsOptionalFeature -Online | Where-Object FeatureName -like '*PowerShell*' |
  Select-Object FeatureName, State

On Windows 10/11 you'll see MicrosoftWindowsPowerShellV2Root and its nested MicrosoftWindowsPowerShellV2. The 2.0 engine is hosted inside powershell.exe (5.1) — it is not a separate process — so the only way it actually runs is something invoking powershell.exe -Version 2 (or -V 2).

2. Find anything still using the 2.0 engine

Look for processes started with -Version 2:

Get-CimInstance Win32_Process -Filter "Name = 'powershell.exe'" |
  Where-Object { $_.CommandLine -match '-[Vv]ersion\s+2\b' } |
  Select-Object ProcessId, CommandLine

Also check legacy scheduled tasks and services that reference powershell -version 2:

Get-ScheduledTask | Where-Object {
  ($_.Actions | ForEach-Object Execute) -match 'powershell' -and
  ($_.Actions | ForEach-Object Arguments) -match '-[Vv]ersion\s+2\b'
}

3. Disable it

From an elevated PowerShell:

Disable-WindowsOptionalFeature -Online -FeatureName MicrosoftWindowsPowerShellV2Root

This disables the whole subtree; a reboot may be required. It only removes the 2.0 engine — your powershell.exe (5.1) and PowerShell 7 are completely unaffected, so the 5.1 fallback you mentioned keeps working.

4. Verify

Get-WindowsOptionalFeature -Online | Where-Object FeatureName -like '*PowerShell*'

Both features should now report Disabled. If some legacy script genuinely needs the engine, it will fail with an explicit "Windows PowerShell 2.0 is not installed" style error — which is the point: you want that to surface during testing rather than silently running on an unpatched engine.