Better filters for the trader would be awesome! I have no problem with cross tier trades being allowed, though. As for players who routinely post 0-1 star trades? I just learn who they are and don't take any of their trades, even good 3* same-tier trades. It does make taking trades outside the FS take longer. And, I never trade on the mobile app. Either my fat fingers or the change in how trades reset as opposed to browser makes it too likely I'll make a mistake, so I just don't do it.
I'm only talking T1, 2, and 3 goods here, not Sentients which can be different. Sentients are also traded world-wide, not just in the discovered neighborhood meaning a larger range of different trading styles.
I don't take cross tier trades (other than to help FS members), but I like them being available to use when an FS member needs help. My reasons are not the perceived value of those trades. I do it because my cities are designed to produce goods sustainably balanced within each tier. I may have fewer T3 goods than T1 goods, but the game does not require as many T3's so it's balanced even though they're not equal amounts. Also, I am lucky to have had a few years of play prior to the Moonstone set wreaking havoc with the balance in T2 goods. So, yes, I have 63million scrolls in this crystal boosted city, but crystal/silk are balanced at around 8mil each. Routinely taking even good 3* cross trades makes it really difficult to maintain the balance I like within each tier. Yes, with effort, I could do it, but it's not how I prefer to play, so I'm not gonna do it