1. It rewards exploration because you have to explore the safari zone to find it lol. So it is very much an exploration reward.
2. You completely missed the point. Houndour was never meant to be used for clearing the normal in game story. (Which by the time you get to Kanto is really just fanservice to walk through and enjoy exploring with the team you already beat the E4 with) It was meant to be something cool to find later to use in the tower and in pvp. Not everything is made for the "storyline" gameplay part of the game. There is more to the game, something that is very very very clear that a lot of you do not understand. Which was the second half of that quote that you decided to ignore; instead trying in invalidate something that was clearly intended for a purpose different then what you play the games for.
So, let's talk about the Johto pokemon and what they're for.
152-160: Starters, you can use one family per playthrough.
Sentret, HootHoot, Ledyba, Spinarak, Hoppip, Aipom, Sunkern, : Derps. Fine early-game, but you want them replaced by the E4.
Chinchou, Natu, Mareep, Sudowoodo, Girafarig, Pineco, Quilfish, Heracross, Teddiursa, Swinub, Corsola, Phanpy, Stantler, Hitmontop, Miltank: Fine
Crobat, Bellossom, Espeon, Umbreon, Blissey: Evo of a Gen 1 mon you're likely bored with
Pichu, Cleffa, Igglybuff, Tyrogue, Elekid, Magby, Smoochum: Baby of a Gen 1 mon you're likely bored with.
Togepi, Unknown, Wobbuffet, Shuckle, Delibird, Smeargle: Gimmick
Slowking, Politoed, Scizor, Steelix, Kingdra, Porygon 2: Trade evo
Misdrevous, Murkrow, Slugma, Sneasel, Houndour, Larvitar: Kanto-only
Dunsparce, Snubbull, Marrill, Yanma, Remoraid, Mantine, Skarmory: Stupid-rare
Raikou, Entei, Suicune, Lugia, Ho-oh, Celebi : Legendary
Now, that list isn't perfect, there's a lot of stuff that can fit in multiple categories, and I'm pretty sure I changed my definition of stupid-rare at some point. That said, I tried to be as generous as possible(as evidenced by including Sudowoodo and Corsola in the 'fine' category instead of gimmick or derp). And definitely, there's playthroughs and players who can justify most of these. A 10% chance of finding a mon in a single body of water you have no reason to linger in isn't a reasonable thing for most 10 year olds, but it's simple with a guide, after all. But that's a pretty short list of new mons that are usable for the majority of the game. And like it or not, the actual story is what most players are going to play through.
Going from 150 new mons, many of which are perfectly usable, to 100 new mons, many of which are gimmicks, intentionally stupid to get, weak, or not actually new, is not going to make people happy. And if you like the games(like I do) and replay them a reasonable amount, I very quickly get bored of "well, I've got 4 kanto mons+my starter, time to grind for the one Johto mon I haven't used repeatedly before. Hope that 1% chance comes up soon!" It's just especially noticeable with the Kanto-only mons because they are impossible to use in-game without trading and are clearly designed to be things people want. The only non-Umbreon dark types, the only new Ghost-type, the Pseudo-legend, and Slugma...these are things people were clearly going to be interested in, and GF made sure you couldn't use them for what people ostensibly bought the games for.