Definitely not trying to do that. To speak on the idea of visible, inaccessible DLC in a game, it is bad, full stop. I think it's certainly cynical of the developers to put the doors there and not completely remove them unless you have the DLC installed.
Seeing those seams is something you can't help but notice, and it absolutely does impact your perception of the game to have them there. What I am saying is that Dead Cells is so thoroughly well made and considered that I was able to tell myself "these doors are locked until I beat the game on a certain boss cell and feel justified to pay for an 'expansion' and access new content".
I can live with that specifically because the doors are not necessary, you just can't enter them and take a different path, similar to other locked zone doors that are instead locked because of boss cell requirements. The maps are also consistently laid out in terms of direction to get to a certain zone entrance, so once I know it's there I can avoid that path in the future until I decide to stop playing or buy more content.
If Dead Cells were a lesser game I would be much less forgiving about it, and to be clear, again, the fact that you can see DLC doors for DLC you don't have is bad design, full stop. It's just that the game is so good overall, I think it'd be sad for someone to pass it up for that reason, or to think that they're not getting enough because of it. It's a shame, but the game's still awesome.
I don't think you're wrong to feel the way you do, but try not to sleep on the game because of it. Even without the paid DLC the base game and free updates have a lot of mileage.
I love the series! I hope you enjoy.