ash&charizardfan
Humans are tools
Yeah, back then the writers just didn't consider it a new series and the episode number continued after Orange Islands into it. Same reason Ash/Misty/Brock didn't get new clothes, etc.
But yeah Johto is very different from Kanto or Orange Islands. And when people think of the nostalgia OS they think of Ash with Bulbasaur/Squirtle/Charizard, not his Johto team of Bayleef/Cyndaquil/Totodile/Noctowl...his Johto pokemon are virtually never remembered in the same manner as Ash's Kanto pokemon are when people think of the nostalgic OS.
Whole kanto, OI and johto are considerd part of one series, i think kanto was part of anime showing what pokemon world is, they didn't planned it for a long series i think anime series was planned for 82 episodes, whereas OI was a short stopgap until johto series started (probably that's why ash was given a win) while johto was the start of the regional formula which is going on still now which basically focussed on ash challenging the gyms trying getting to the league.
Johto is considered the part of OS, its different only because thise region started having main focus on battling aspects rather than humour and fun. Ash's bayleef is still remembered by many people its just his johto pokemon were less iconic than his kanto trio, also johto is less memorable than kanto mainly because it was boring for the most parts ash's team was underdeveloped, gary despite being main rival only appearing once or twice and his companions misty/brock becoming bland and regressing to background characters.