Hex will always use the same argument that was there before the Lizzy line when it was questioned against the Piccadilly line of which was that it was said to compete with Black Cabbies to Heathrow both in pricing, ease of use and timing. Whilst the Elizabeth line has its pros its been notoriously unreliable for some time after the whole central core running which if the signaling issues that are an ongoing issue aren't fixed will get worse when the Shenfield trains(which were already one of the biggest causes of the delays) end up on all 3 signal systems in May as the line bolsters up to 24 trains an hour with Shenfield's running past Paddington to Heathrow and co.
It all depends honestly on the traveler, I personally already plan my journeys that include traveling fees, when you've just had a long haul flight in after delays etc you're most likely looking for a bit of comfort and somewhere to store luggage and a journey into London that is as fast as possible if need be. Ofc if you have time to burn, don't mind possibly sharing a train that will start getting packed up into Paddington and need to go past London towards Canary Wharf, stratford etc then the Elizabeth Line makes more sense price and comfort wise as you'll be seated at least well before Paddington.
All depends, doubt HEX is going anywhere too soon.
I do agree with your concerns, the over-crowding is a problem (A nice one to have) - lets see how going to every 15 minutes (t4) helps the Elizabeth line.
But I have use the HeX for the last time, not only because of price but also speed.
Using Hex,
Hex to Paddington
Walk to Hammersmith and City line
Tube to Kings Cross
Train to Welwyn Garden City.
(I could also Tube to Finsbury Park which can feel to take about the same time if I get a bad transfer from Paddington)
Now,
Train to Farringdon / Liverpool street
Train to Welwyn Garden City.
The journey is much quicker and less trouble. Farringdon is easier to change at as the walk at Moorgate feels long, but is OK.
I am sure readers can give many example where they can get to their destination with a single change now. We may not be the target customers for HeX, but I can’t see anyone that can now do a single change at Farringdon / Liverpool Street going back to HeX.
Will it go, probably not, will it remain at every 15 mins, probably no either.