Obviously it did in some aspects,thought it got worse in others.
In positive sense anime over the years improved in characters getting more development.
Anime wasn't anymore centered mostly around Ash as only central character with others being allowed to have their stories fleshed out more. Battling improved a lot since early days with more details and strategy being implemented into it. In Kanto aside from few battles(like
Charizard vs Blain
Magmar)most battles in reality were bad.
Group pokemon started to receive more screen time with their characters being fleshed out more. Aside from Ash Kanto starters, Misty
Psyduck and
Togepi almost none of twerps pokemon including TR had their personalities exploited out.
Pacing also got better, and i don't even need to mention how rivalries were handled by miles better compared to Kanto days when Gary appeared in few and far between episodes. Although it wasnt until Sinnoh that writers started treating rivals right(Paul comes to mind).
However it also declined in some aspects since Kanto days, with older seasons having more humor, better dynamic within cast and many things which today would never manage to pass under radar like it was case before. Such exaggerated style and wacky plots original series used to had also resulted in this era of pokemon being known for highest number of banned episodes to this date. Simply because some scenes weren't suitable for kids TV show.
Chemistry and interaction between original trio was also probably most memorable group and one with most synergy. They really felt like genuine group of friends fulfilling each other nicely contributing to fčlamboyant and comic interaction.
Back than, especially in Kanto anime was initially intended to be like family show written for all kind of generations according to
Takeshi Shudo blogs. However since he wasn't allowed to do that, having to adjust to future games and marketing that style of writing started to gradually decline, just to end up disappearing completely somewhere around Hoenn.
What i liked about Kanto,Oi and to lesser extent Johto is also fact how back than writers stick in much smaller amount to games straying away from it quite a few times including less game characters, with more anime exclusive things being incorporated. Nowadays we don't get anymore such unique mini arcs like it was case with Sabrina, St.Anne,
Gengar and
Alakazam bringing in danger whole world, having something like Whirl Islands arc which felt like mini season put in one bigger . Or Giovani gym which involved
Mewtwo following movie canon closely. We don't get whole anime only seasons like it was case with Orange Islands having unique portrayal of gyms and place in which story was set in.
Nowadays pokemon handles main characters better, storyline is more consistent and battles, villains and treatment of pokemon themselves have better writing behind it. However OS had more comedy, better dialogue and dynamic, and wacky and out of place plots with writers seeming to have much more liberty back in day, to spread wings of creativity and use their own imagination.
Misty? who cares. She should stay in her gym forever and never return.
Apparently many fans do care, wanting her back to main cast. Personally i wouldn't mind her return. She was fun character and you could tell there was left untapped potential to do more. Such as her goal of becoming water pokemon master which can't be achieved at gym, providing plausible directions to take it forward and do follow up(benchmarks similar to Whirl Cup which measure someone growth, becoming E4 water trainer etc are some of possibilities).