public CIMRenderer Renderer {get; set;}

{
    IEnumerable<FeatureLayer> featureLayers = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>()
      .Where(l => l.ShapeType == esriGeometryType.esriGeometryPoint);
    var layerFile = @"C:\Data\SDK\UniqueValuePointLayer.lyrx";
    foreach (var featureLayerToSymbolize in featureLayers)
    {
        //Get the Layer Document from the lyrx file
        var lyrDocFromLyrxFile = new LayerDocument(layerFile);
        var cimLyrDoc = lyrDocFromLyrxFile.GetCIMLayerDocument();

        //Get the renderer from the layer file
        var rendererFromLayerFile = ((CIMFeatureLayer)cimLyrDoc.LayerDefinitions[0]).Renderer as CIMUniqueValueRenderer;

        //Apply the renderer to the feature layer
        //Note: If working with a raster layer, use the SetColorizer method.
        featureLayerToSymbolize?.SetRenderer(rendererFromLayerFile);
    }
}