brand new webrowsers dont like old flash/java
heck even old html tags dont work any more like <marquee><nobr><no embed> to name a few
Lol. That's the corresponded to soft forks. Invalidating the valid.
old webbrowsers dont understand DIV CSS or the latest media players
No, they can't, because there have been rules added on top. They can still do the essential; browse the web, but their browsing is very limited. Reminds me of a pre-SegWit node analogy to me.
by the way nodes made pre 2016 do not store full blockdata nor are part of the block or tx relay of all bitcoin users. they are instead via newer nodes handed a striped out version of blocks where old nodes cant fully validate all transactions nor propagate full blocks
I know. I'm aware that if you spin up a v0.1-v0.2.9 node, you can't reach the tip. I'm not quite sure if you could even reach it with any Core client prior v0.8. There have been some technical changes, but the protocol has not introduced any non-backwards compatible rules.
this is not about sustainability. its about breaking security
I don't know what Bitcoin you use, but mine is pretty secure.