diff --git a/src/Avalonia.Base/Diagnostics/StyleDiagnostics.cs b/src/Avalonia.Base/Diagnostics/StyleDiagnostics.cs
deleted file mode 100644
index 3db48cd69c..0000000000
--- a/src/Avalonia.Base/Diagnostics/StyleDiagnostics.cs
+++ /dev/null
@@ -1,37 +0,0 @@
-using System;
-using System.Collections.Generic;
-using Avalonia.Metadata;
-using Avalonia.Styling;
-
-namespace Avalonia.Diagnostics;
-
-[PrivateApi]
-[Unstable("Use StyledElementExtensions.GetValueStoreDiagnostic() instead")]
-public class StyleDiagnostics
-{
-    /// <summary>
-    /// Currently applied styles.
-    /// </summary>
-    public IReadOnlyList<AppliedStyle> AppliedStyles { get; }
-
-    public StyleDiagnostics(IReadOnlyList<AppliedStyle> appliedStyles)
-    {
-        AppliedStyles = appliedStyles;
-    }
-}
-
-[PrivateApi]
-[Unstable("Use StyledElementExtensions.GetValueStoreDiagnostic() instead")]
-public sealed class AppliedStyle
-{
-    private readonly StyleInstance _instance;
-
-    internal AppliedStyle(StyleInstance instance)
-    {
-        _instance = instance;
-    }
-
-    public bool HasActivator => _instance.HasActivator;
-    public bool IsActive => _instance.IsActive();
-    public StyleBase Style => (StyleBase)_instance.Source;
-}
diff --git a/src/Avalonia.Base/Diagnostics/StyleValueFrameDiagnostic.cs b/src/Avalonia.Base/Diagnostics/StyleValueFrameDiagnostic.cs
index 2b0d6c3c64..27683dbe72 100644
--- a/src/Avalonia.Base/Diagnostics/StyleValueFrameDiagnostic.cs
+++ b/src/Avalonia.Base/Diagnostics/StyleValueFrameDiagnostic.cs
@@ -39,7 +39,4 @@ internal class StyleValueFrameDiagnostic : IValueFrameDiagnostic
             }
         }
     }
-
-    [Unstable("Compatibility with 11.x")]
-    public AppliedStyle AsAppliedStyle() => new AppliedStyle(_styleInstance);
 }
diff --git a/src/Avalonia.Base/Diagnostics/StyledElementExtensions.cs b/src/Avalonia.Base/Diagnostics/StyledElementExtensions.cs
deleted file mode 100644
index 78ab52a6bc..0000000000
--- a/src/Avalonia.Base/Diagnostics/StyledElementExtensions.cs
+++ /dev/null
@@ -1,24 +0,0 @@
-using System;
-using System.Linq;
-using Avalonia.Metadata;
-using Avalonia.Styling;
-
-namespace Avalonia.Diagnostics;
-
-/// <summary>
-/// Defines diagnostic extensions on <see cref="StyledElement"/>s.
-/// </summary>
-[PrivateApi]
-public static class StyledElementExtensions
-{
-    [Obsolete("Use AvaloniaObjectExtensions.GetValueStoreDiagnostic instead", true)]
-    public static StyleDiagnostics GetStyleDiagnostics(this StyledElement styledElement)
-    {
-        var diagnostics = styledElement.GetValueStore().GetStoreDiagnostic();
-        return new StyleDiagnostics(diagnostics.AppliedFrames
-            .OfType<StyleValueFrameDiagnostic>()
-            .Select(f => f.AsAppliedStyle())
-            .ToArray());
-    }
-}
-