So let's compare the hangover years after the last 2 halving pumps.
you are looking at things in a very simplified way by using halving as a point of reference for a 4 year long period! no market is affected by one cause like halving like this for 4 years!
2014: the year of the alts, every week several coins would pump 10x+, some pumped 100x in a week or 2. Exchanges were free to use anonymously.
1. from the early days that altcoins were created with the goal of being pumped and dumped we are having big altcoin pumps nearly every day. it has never been consistent 10x per day but pretty close to it and it is still happening as we speak today.
2. again from early days whenever an exchange needed to work with fiat and banks they were asking for KYC because that was required of them. these days in some countries regulations are becoming more serious but I don't see your point in mentioning this here!
The alt scene it completely dead, if a coin goes up by 2x over a month that is a huge deal. Trading alts to make more bitcoins is nothing but a memory.
the alt scene is pretty much the same bullshit as ever. just because YOU don't see more than 2x pumps over a month that doesn't mean they aren't happening. of course the 2017 pumps has left most of them damaged and still dumping but the big pumps are still happening because the pumpers still want money and there are enough newbies left to scam.
What is the result of these differences - is it possible bitcoin will never pump again due to crypto trading action being permanently dead and trading becoming so difficult and transparent it's no longer worth playing with?
bitcoin will never pump again. in fact it has been about 5 years that bitcoin is not pumpable because the market has grown big enough that prevents any "pump" from happening. besides bitcoin is not some pump and dump shitcoin that you can pump!
none of the things you said so far has anything to do with bitcoin though! bitcoin price will continue to rise as its adoption is going to continue to grow. with more demand and its scarce supply that is inevitable.
but no it will never be pumped again. 2013 was the last time we saw a pump performed by Mt Gox.