Or there's 1. e4 e5
2. Nf3 Nc6
3. Bb5 a6
4. Ba5 b5
5. Bb3 Nf6 to avoid 5.d4 which can be annoying. (6.Ng5 doesn't work because of d5 and Nd4)

Probably still an OK defense but most players now days maybe feel it's too loose. Black does get pieces out and can apply some pressure but can face some uncomfortable issues.

White's e5 pawn often ends up pretty stable and can be a pain for black to play around. It can also often end up being useful to white later on.

Sometimes black's c-file can be vulnerable as well as his kside with the N gone and e-pawn restricting the DSB.

Altogether, even with active pieces black's usually still on the defensive and can't really feel comfortable about keeping control of the situation.

Korchnoi, who didn't mind dynamic games, might be most famous Ruy Open player with all those games against Karpov. But I remember Ding Liren played it a bit awhile back and Koneru has it in her rep on the women's side. Here's a couple of games that maybe show some of white's ideas:

Yifan Hou vs Koneru, 2012

Yeah but compare it to the Caro-kann. In the classical Caro, you contest the center with two passive pawn moves, losing time, then you bring out the light squared bishop which gets harrassed and or traded, aiding white's development further. The Caro-kann is basically a game of trying to catch up in development before white throws a sledgehammer, and even in the main lines, the structures invariably favors white in any middlegame.

Now in the Open Ruy, black has less concessions, pieces get out without losing time, and the structure long term is solid. White has a normal advantage for an 1.e4 type structure. Nothing more, nothing less.

Ideas are probably really different. Typical Caro usually has black looking for at first a solid structure at cost of being cramped. Then exchanging pieces with the view of eventually breaking out at least somewhat. The whole thing is predicated on not giving up too much while keeping control. This is somewhat the same idea in the closed Ruy.

Open Ruy seems to look to have less solid structure but gets pieces out and more dynamic play. This dynamic play usually means less confidence in keeping control.

Caro might be more common because players today are probably more comfortable with keeping control as much as possible until clear advantage can be seen.

Caro players today and in the past have probably never liked White play that opens up lines or push with kside pawn storms early. These rushes typically cause black to make adjustments that usually end up feeling like the position could be tipping out of control.

That's exactly why I try not to play the Caro against those who've played the advanced with g4 or h4 lines and Panov specialists.

Even without agressive play, black is lagging behind development and has conceded greater space to white's minor pieces, really regardless of the variation white chooses. It's a passive defense that only Anatoly Karpov has been able to use to good effect at the highest level. You will note that he did not believe in it enough to use it as his standard defense in the Kasparov matches, only whipping it out occasionally.