If the brand is a Silverback with the cathedral slide out, then yes it would be a deal breaker for me. Having a curb side slide out that dumps water directly at the door makes zero sense. Why have an awning that could provide rain protection but a slide out that totally defeats that function? Some owners report water problems inside the RV if they need to retract the slide while it is raining. And there is no way to add toppers that might minimize the problem.
Any unit I buy must have toppers. The slide out roof has less insulation, so toppers help in the summer, both in overall cooling and less temperature variation around the RV. And I prefer to retract the slide outs any time I want, not just after the roof has been cleaned.