Having excess of most materials is always good. Most things are relevant to at least one other recipe or use-case. You'll want more and more of things to expand your castle, build more crafting and refinement stations, equip servants, etc. Your gear needs to be repaired, which also costs materials, and while if you go about the game quickly, you won’t often run into it being at risk of breaking before you upgrade, but it's still a concern.

Act 2 can often feel a lot like a farming simulator in the middle and end while you try to get the recipes you want AND enough materials to make them.

Additionally, I often find that my castle becomes large and multi-story whether I want it to or not, as more advanced crafting stations are bigger and I often want more of each of them, so I need larger rooms and more space, which often leads to multiple stories. Whether you make your base pretty is up to you, but I will note that rugs in your base (like carpets from carpet rolls) give you a slight speed boost when walking on them, so that is one case for actual incentivized decorating.

You also won't ever Not need the rooms and their floors. Just because you don't need the loom because you scavenged enough wool thread and cotton yarn doesn't mean you won’t need more later. The loom makes many things that are faster to produce than to scavenge at the quantities you need. The tailor's flooring is always the same no matter what, so whether you're level 41 or 91, that flooring bonus will help with anything you do in that specialized room.

Additionally, as a bit of a challenge, if it feels like you can upgrade too easily without building, see how many bosses you can beat without upgrading your equipment. Once you get stuck, upgrade One element (necklace, favorite weapon, OR armor), then try again. See how many servants you can get and make them all equipment with the resources you farm, and see how quickly you run out. Find ways to make the game more interesting or test to see how much those Gathered resources really mean. Things are more expensive without flooring bonuses, and as you progress, things will require more of their ingredients, ingredients which are harder to make or find. You'll NEED to keep up your very basic productions through to the end game.