before the junk data of appended data after signature
there was op_return
but this too was not used as a data exploit in 2009-2014
https://bitcoin.org/en/release/v0.9.0#rebranding-to-bitcoin-coreback then core pretended to be against wanting bitcoin to be used as a junk data exploit, yet, stupidly opened the exploit to allow 40byte(later 80) and then others opcodes were added(pushdata) that allowed 520, then others allowing uto 4mb using a different opcode. and other(opsuccess) aded more recently to make it now have hundreds of opcodes that can be abused
it has never "always been possible"
it has only been possible since core jumped in and changed things
Before OP_RETURN exist, people exploit Bitcoin address to store arbitrary data which bloat UTXO.
It's also not correct to blame developers, because other blockchains that do not follow the same code as Bitcoin are also plagued with silly pictures. This stuff would exist regardless of what developers have or haven't done. The only thing that would be different is the quantity of silly pictures. There's room for more of them in Bitcoin versus coins like DOGE, where they can't affordably spam as many of them.
Less quantity of arbitrary data is better than nothing. And IMO not adding 10000 bytes limit on Taproot script is a mistake, when such limit exist on different kind of script.