Ohhhhh I couldn't cook in one that had baked on food and couldn't see through the glass. We moved into our place and the oven had never been cleaned. I tried everything including the toxic stuff that burns your eyeballs and was still disgusting so I didn't use the oven until we got a new kitchen 6mo later.
I wipe the glass after every use. Whilst hot any splatter comes straight off.
I blame my mum, she is a clean freak