I completely understand the distinction. However, If I don't want to help relay someone's garbage transactions, I should absolutely have the option to block them from my node's mempool. However, if those transactions manage to reach a miner's node and get included in a block, my node is obligated to accept that block to stay in consensus.

These are node policy settings, not consensus rules, so it's up to each node operator to decide what they want to relay or not. Ultimately, the miners' nodes are the ones that really matter here -- and they'll most certainly relax their limits to maximize fee revenue.

That said, everyone has the right to protest by making the relay of such data less efficient. By enforcing their own relay policies, non-miner nodes can slow down the spread of unwanted transactions -- not to actually stop them, of course, but more to get that warm fuzzy feeling of "I'm doing my part for the network."

Furthermore, I tend to believe that this kind of data exists largely due to a lack of real economic competition on the blockchain. In the grand scheme of things, hardly anyone actually spends BTC, so spamming is relatively cheap. Fast forward a few decades, and that kind of behavior, along with even small-value transactions, will likely become economically unviable. Trends like BRC-20 are short-lived by nature. I also think a lot of this isn’t done purely to spam; people are often just experimenting or having fun. Paying real, scarce BTC just to "spam" isn't something a normal person would do. If I inscribe my photo on the most robust blockchain out there, sure, that might be a fun experiment --but I'm not paying $5 every day just to keep doing it.