As I get further into the game I have to say that it looks pretty ugly at times. The outdoor environments, at least.

Well, that depends on how you're defining "looks as good as". If you particularly love the style of presentation in those games there's certainly nothing on Switch in the same vein, simply because nobody has tried it, at least not with anywhere near the same level of investment of resources.

On the other hand, Switch games like Hellblade and Doom are more technically advanced than UC2 or TLOU by a significant amount, largely by virtue of using mostly PS4 tier rendering techniques.

Decent conversion but it massively helps that their using pre-rendered cutscenes and omitting the GI solution ...

Might want to use gameplay instead of cutscenes for comparisons ...

Great news for Switch owners. Its good to see ports doing extremely well on Switch.

So looking at the presentation level, what is seem by people and not what/how it is done, the point made that PS3 or X360 could have Hellblade executed there and having acceptable result that looks alike the Switch result is true.

It may not have the same techniques, but if someone were willing to make the port they could.

Which is the same situation on whenever we are discussing ports to Switch, any game launched on PS4/X1 could be released on Switch, and that isn't because it is almost as powerful or have similar technology. It's because it is at least on a level that if dev wants to take the very long time and cost they could make even RDR2 work on Switch (and still look alike). But most ports won't happen because the level of work is just to high to be justified.

PS3/360 could've had a version of Hellblade, in the sense you can port almost anything to anything if you modify it enough; see last gen when the PS3/360 Call of Duty games were brought to the Wii.

But a PS3/360 port of Hellblade would looked quite unlike the Switch version. 

Rendering techniques aren't just technical buzzwords, they have a key role in how a game looks.

They would look different, sure. As well as Switch looks quite different than PS4 version.

You can use different techniques, less taxing and still come to a decent result.

But since a theoretical PS3 version would look worse than the Switch version, that ultimately doesn't change the fact that Hellblade on Switch is more graphically advanced than the PS3 games you claim look better than anything on Switch.

That would be true. Although to be sure I would have to compare Hellblade Switch to UC2 or TLOU side by side on same size TV.

But since Switch have more power than PS3 certainly it can put better graphics than it when used for it.