diff --git a/narwhals/_polars/utils.py b/narwhals/_polars/utils.py
index e51852f532..0a9a586fce 100644
--- a/narwhals/_polars/utils.py
+++ b/narwhals/_polars/utils.py
@@ -23,7 +23,6 @@
     from narwhals._polars.expr import PolarsExpr
     from narwhals._polars.series import PolarsSeries
     from narwhals.dtypes import DType
-    from narwhals.typing import TimeUnit
     from narwhals.utils import Version
 
     T = TypeVar("T")
@@ -70,16 +69,14 @@ def extract_args_kwargs(args: Any, kwargs: Any) -> tuple[list[Any], dict[str, An
 
 @lru_cache(maxsize=16)
 def native_to_narwhals_dtype(
-    dtype: pl.DataType,
-    version: Version,
-    backend_version: tuple[int, ...],
+    dtype: pl.DataType, version: Version, backend_version: tuple[int, ...]
 ) -> DType:
     dtypes = import_dtypes_module(version)
     if dtype == pl.Float64:
         return dtypes.Float64()
     if dtype == pl.Float32:
         return dtypes.Float32()
-    if dtype == getattr(pl, "Int128", None):  # type: ignore[operator]  # pragma: no cover
+    if hasattr(pl, "Int128") and dtype == pl.Int128:  # pragma: no cover
         # Not available for Polars pre 1.8.0
         return dtypes.Int128()
     if dtype == pl.Int64:
@@ -90,7 +87,7 @@ def native_to_narwhals_dtype(
         return dtypes.Int16()
     if dtype == pl.Int8:
         return dtypes.Int8()
-    if dtype == getattr(pl, "UInt128", None):  # type: ignore[operator]  # pragma: no cover
+    if hasattr(pl, "UInt128") and dtype == pl.UInt128:  # pragma: no cover
         # Not available for Polars pre 1.8.0
         return dtypes.UInt128()
     if dtype == pl.UInt64:
@@ -113,32 +110,32 @@ def native_to_narwhals_dtype(
         return dtypes.Enum()
     if dtype == pl.Date:
         return dtypes.Date()
-    if dtype == pl.Datetime:
-        dt_time_unit: TimeUnit = getattr(dtype, "time_unit", "us")
-        dt_time_zone = getattr(dtype, "time_zone", None)
-        return dtypes.Datetime(time_unit=dt_time_unit, time_zone=dt_time_zone)
-    if dtype == pl.Duration:
-        du_time_unit: TimeUnit = getattr(dtype, "time_unit", "us")
-        return dtypes.Duration(time_unit=du_time_unit)
-    if dtype == pl.Struct:
-        return dtypes.Struct(
-            [
-                dtypes.Field(
-                    field_name,
-                    native_to_narwhals_dtype(field_type, version, backend_version),
-                )
-                for field_name, field_type in dtype  # type: ignore[attr-defined]
-            ]
+    if isinstance_or_issubclass(dtype, pl.Datetime):
+        return (
+            dtypes.Datetime()
+            if dtype is pl.Datetime
+            else dtypes.Datetime(dtype.time_unit, dtype.time_zone)
         )
-    if dtype == pl.List:
+    if isinstance_or_issubclass(dtype, pl.Duration):
+        return (
+            dtypes.Duration()
+            if dtype is pl.Duration
+            else dtypes.Duration(dtype.time_unit)
+        )
+    if isinstance_or_issubclass(dtype, pl.Struct):
+        fields = [
+            dtypes.Field(name, native_to_narwhals_dtype(tp, version, backend_version))
+            for name, tp in dtype
+        ]
+        return dtypes.Struct(fields)
+    if isinstance_or_issubclass(dtype, pl.List):
         return dtypes.List(
-            native_to_narwhals_dtype(dtype.inner, version, backend_version)  # type: ignore[attr-defined]
+            native_to_narwhals_dtype(dtype.inner, version, backend_version)
         )
-    if dtype == pl.Array:
-        outer_shape = dtype.width if backend_version < (0, 20, 30) else dtype.size  # type: ignore[attr-defined]
+    if isinstance_or_issubclass(dtype, pl.Array):
+        outer_shape = dtype.width if backend_version < (0, 20, 30) else dtype.size
         return dtypes.Array(
-            inner=native_to_narwhals_dtype(dtype.inner, version, backend_version),  # type: ignore[attr-defined]
-            shape=outer_shape,
+            native_to_narwhals_dtype(dtype.inner, version, backend_version), outer_shape
         )
     if dtype == pl.Decimal:
         return dtypes.Decimal()
@@ -157,7 +154,7 @@ def narwhals_to_native_dtype(
         return pl.Float64()
     if dtype == dtypes.Float32:
         return pl.Float32()
-    if dtype == dtypes.Int128 and getattr(pl, "Int128", None) is not None:
+    if dtype == dtypes.Int128 and hasattr(pl, "Int128"):
         # Not available for Polars pre 1.8.0
         return pl.Int128()
     if dtype == dtypes.Int64:
@@ -200,24 +197,22 @@ def narwhals_to_native_dtype(
         return pl.Datetime(dtype.time_unit, dtype.time_zone)  # type: ignore[arg-type]
     if isinstance_or_issubclass(dtype, dtypes.Duration):
         return pl.Duration(dtype.time_unit)  # type: ignore[arg-type]
-    if dtype == dtypes.List:
-        return pl.List(narwhals_to_native_dtype(dtype.inner, version, backend_version))  # type: ignore[union-attr]
-    if dtype == dtypes.Struct:
-        return pl.Struct(
-            fields=[
-                pl.Field(
-                    name=field.name,
-                    dtype=narwhals_to_native_dtype(field.dtype, version, backend_version),
-                )
-                for field in dtype.fields  # type: ignore[union-attr]
-            ]
-        )
-    if dtype == dtypes.Array:  # pragma: no cover
-        size = dtype.size  # type: ignore[union-attr]
+    if isinstance_or_issubclass(dtype, dtypes.List):
+        return pl.List(narwhals_to_native_dtype(dtype.inner, version, backend_version))
+    if isinstance_or_issubclass(dtype, dtypes.Struct):
+        fields = [
+            pl.Field(
+                field.name,
+                narwhals_to_native_dtype(field.dtype, version, backend_version),
+            )
+            for field in dtype.fields
+        ]
+        return pl.Struct(fields)
+    if isinstance_or_issubclass(dtype, dtypes.Array):  # pragma: no cover
+        size = dtype.size
         kwargs = {"width": size} if backend_version < (0, 20, 30) else {"shape": size}
         return pl.Array(
-            inner=narwhals_to_native_dtype(dtype.inner, version, backend_version),  # type: ignore[union-attr]
-            **kwargs,
+            narwhals_to_native_dtype(dtype.inner, version, backend_version), **kwargs
         )
     return pl.Unknown()  # pragma: no cover