Nothing in Colorado law required the landlord to volunteer information on what it would take to change the filter. Again, if that was a concern to you, you should have asked about it. Like it or not, you are the one that must protect yourself. Don't expect that of the landlord. Read the proposed lease and understand all that it requires you to do and what the landlord will do. If anything in it is not to your liking, try to negotiate something you do like. Then once you've gotten to the point the landlord will not budge on anything, you have to make the choice of whether to take the lease. If you do, then you at least are going into it knowing what you are obligated to do. You don't have to like every provision in the lease, but the landlord certainly may hold you to the lease.
It's a realistic point of view. Yes, all along the front range housing has gotten expensive, and it's harder to find affordable housing at the lower income end. But in Colorado Springs you weren't limited to just this one apartment in the whole city to choose from. If you had really wanted other options, you could have found something else. Maybe not a lot of choices, but they are there. But regardless, none of this changes the legal issue at all. Trouble finding an affordable place does not alter contract law. You're still obligated to your end of the bargain once you enter into the lease. Colorado landlord-tenant law is pretty basic and for the most part lets tenants and landlords work out between them what the deal is going to be.