As a long time RS2 player and someone who also played quite a bit of HLL I wouldn't recommend it personally. RS2 still has a strong playerbase so I'd just go back to it. They didn't at all fix the problem of enemies being impossible to see, in HLL everything was just so grey that I would never be able to see anyone at all. It really made me appreciate how good RS2 is in that regard where every element, from the sound design to the visuals to the actual game information, is giving you clues as to which bush is hiding a GI in it.

And you might say "But thats just camouflage its realistic" but HLL makes no other attempts at realism. Its whole niche is that its just one rung above a regular arcade shooter in realism terms. Its also yet another unoptimised UE5 bloat game. Finally while the tunnel mechanics are a interesting design, they require actual teamwork. Anyone who has played HLL knows that even a basic level of co-operation cannot be expected from people, which is why I've always appreciated that the co-operation in RS2 is very modular.

My only real issue with RS2 is that the calcification of the playerbase does lead to campaign mode often becoming a steam roll, but its a problem I've never seen a good solution to.