3) Increasing the block size has only limited/reduced access to run Bitcoin full nodes, not ensured it. Node counts have dropped drastically (50%!) since then, and it is clear in retrospect that the block size increase was a huge mistake.

4) The "Bitcoin Independence Day" is only coincidentally related to Segwit. The relevance of it is rejecting control of Bitcoin by miners. Several developers attempted to re-assert miner control over Bitcoin 2 years ago with Taproot (so-called "Speedy Trial"), and it's important to remember what "Bitcoin Independence Day" was all about (and the lessons we supposedly learned) and push back against that to ensure it never happens again.

I didn’t know any of this thanks for sharing!

Thank you for the explanation!

In fact, upon further reflection, it's very important to call this out. Bitcoin independence day is about UASF, _NOT_ about segwit. Making it about segwit distracts from the real meaning and we need to ensure UASF mindset remains prevalent in Bitcoin, especially these days.

Hard to say without knowing the counter factual, e.g. if SegWit was deployed with no discount and the witness data included in the 1 MB limit. We don't know what part of that 50℅ was due to slower sync vs. e.g. just more user friendly wallets (that don't use a full node). Without knowing which of these nodes actually controlled funds vs just astroturfing it's not even clear if the trend is really down.

There's also the UTXO set growth to consider, a problem that takes a bit longer to manifest than block size. SegWit improved the incentive there.

Segwit did improve quite a few things. That fix doesn't require a block size increase.

Without the discount it would still be cheaper to create a new change output than to spend an existing UTXO.

A discount with a 4x decrease for non-witness stuff would also work. That would have been a "bit" controversial though.

It kinda still is, thanks to the block size increase. Without the block size increase, the discount could apply to all transactions