I think it's clear that the intent of The end is to show HOTU is superior to LT.
GS IIRC used to maintain that LT and PF are equal status but play different roles, and both are probably serving TOAA. In each of their areas , they are supreme. PF creates and ends universes, LT maintains then.
So when the time comes for PF to do it job, it will 'win'. It's PF role.
With HOTU, we actually see Thanos with HOTU absorbing LT and all the abstracts *against their will*. So HOTU>LT for sure.
Can PF do it? Possibly, as I understand it, that is the plan of the Stranger , to replace all the abstracts. There is some dispute whether LT is included in their number in this scenario, but let's assume he is included.
As I understand it, and please correct me if I'm wrong, this never really happens though. It's part of the plan but it's not shown ever happening.
So on this point HOTU demostrates a real feat against a possible PF one. Granted a possible feat that seems likely to happen because The stranger thinks it will work.
The replacement of all the abstracts by humanity is one that is the natural part of cycle, it is stated that the abstracts will not fight against it.
In the Long run when PF destroys the universe, and evolved mutants replaces the abstracts it won't be a power struggle, just part of nature.
Thantos with HOTU usperhing that role seems to me to be a much bigger feat since it goes against natural order.
On top of that Thanos may have fought the powers and absorbed the universe but Phoenix killed the universe just like that as a side effect of her Phoenix work.
Does this feat show on panel the absorbing of LT? If not, it's impressive, but in comics it's fairly common to see universes being destroyed. That does not imply that LT is destroyed.
I think the impressive thing about HOTU's feat is not the ending of the universe (which let's face it isn't that rare in comics!) , but we have a straight forward depiction of LT being owned completely.
There are whatifs, and other situations where we see the will of LT being blocked, but AFAIK Thantos with HOTU is the only one where we actually see LT being totally absorbed on screen. That is impressive!
Sure some speculation might sugguest that evolved humans might replace LT (I'm not sure about this point, LT seems to be a different class from Eternity and other abstracts, but let me concede the point here) , but we never see it happen, so it still remains speculation.