Hello @kartik,
Using a modelserializer might be an overkill. This simple serializer & view should work.
Serializers.py
from rest_framework import serializers
from django.contrib.auth.models import User
class ChangePasswordSerializer(serializers.Serializer):
    model = User
    """
    Serializer for password change endpoint.
    """
    old_password = serializers.CharField(required=True)
    new_password = serializers.CharField(required=True)
Views.py
from rest_framework import status
from rest_framework import generics
from rest_framework.response import Response
from django.contrib.auth.models import User
from . import serializers
from rest_framework.permissions import IsAuthenticated   
class ChangePasswordView(UpdateAPIView):
        """
        An endpoint for changing password.
        """
        serializer_class = ChangePasswordSerializer
        model = User
        permission_classes = (IsAuthenticated,)
        def get_object(self, queryset=None):
            obj = self.request.user
            return obj
        def update(self, request, *args, **kwargs):
            self.object = self.get_object()
            serializer = self.get_serializer(data=request.data)
            if serializer.is_valid():
                # Check old password
                if not self.object.check_password(serializer.data.get("old_password")):
                    return Response({"old_password": ["Wrong password."]}, status=status.HTTP_400_BAD_REQUEST)
                # set_password also hashes the password that the user will get
                self.object.set_password(serializer.data.get("new_password"))
                self.object.save()
                response = {
                    'status': 'success',
                    'code': status.HTTP_200_OK,
                    'message': 'Password updated successfully',
                    'data': []
                }
Hope this works!!
Thank You!!