Gen 4 definitely has an issue, we've all gone over the Diamond & Pearl Dex nonsense, but the cross-gen new babies I would not put in that bin. 6 of them were readily available in the wild at decent-to-common encounter rates(Budew is super early & common, Bonsly/Mime Jr are uncommon around hearthome, Chingling hangs out at decent rates near mt coronet iirc, Mantyke is all over the ocean routes, you're given a Happiny egg) and spread throughout the game. Their breeding items were definitely spread around a bit more, but obtaining them wasn't too terrible an ordeal (certainly better than the trade evolution items or stones....).For newer games I don't give such a pass. Especially Gen 4 which add more babies and more stuff to make them difficult to obtain with breeding items.
Munchlax was definitely the worst, what with not jsut being super rare on honey trees (itself, an ordeal to use!) but only on certain honey trees. Unless you were super lucky or patient it was literally better to just trade or port over a snorlax then use the incense method.
And then moving forward they just shove all the incenses into a single shop for you to buy.