I don't know...I kind of find it weird that there' hardly any content on playing AS Yoshi in this sub-forum. A lot of the posts are about other people asking us how to beat...us, rather than any information on how to make ourselves better players. No vods, no tech, no strategy talk, no nothing. I find it odd.
What's happened is that Smashboards is, by and large, a place for entry-to-mid level players to hunt for pieces of information to help improve their game. Since Yoshi as a character has always had a small player base, there are few Yoshis around to drive discussion or discovery. Since the few Yoshis that
are around are entry-to-mid level, they don't really have the knowledge or expertise to generate discussion.
Other, more typically popular characters, will have more players at that entry/mid level, thus more discussion (slightly, anyways). They are also likely to find nothing about Yoshi in particular in their character board and so they come here for help.
Edit: Also, since Yoshi is unpopular and the community is so small, it has become sort of an in-group that has transitioned from game to game. That's also why so much is happening away from here -- the major Yoshis already have the group they will work with and have no need to look here or share anything here.
Most of the higher level discussion/discovery/analysis is held in character Discords now. See below as an example.
I recommend trying the Yoshicord, there are people there willing to give advice and a lot of discussions on MUs and such (if you want to know something specific you can search a key word for it (example: Snake for the Snake MU) and you'll probably find discussion about it.
Message boards have become a thing of the past as far as the Yoshi community (and the Smash community at large) is concerned. It would require the dedication of the individuals in the Discord to share the findings here or shift discussion here, but there's practically no incentive for them to do this.
Part of this could be the increase in competitive games becoming "lifestyles". For competitive Smash, if you want to compete and stay afloat, you need to dedicated an inordinate amount of time to it. That means joining the Discord, staying intensely involved with the players there and forming those connections so they'll actually want to help you. This also requires you to travel to events in person, compete, and get videos to ask for specific advice. You will also typically need to prove yourself as "good" for people to take you seriously and want to spend serious time on you.
In the past, discussion would happen on Smashboards with dedicated threads and topics that were easy to access and find, and did not require you to find an elusive link/invite to a Discord chat somewhere. Things were shared for everyone's benefit publicly and easily. That's just not the case anymore.
So anyways, if you're looking for tips and tricks about playing
as Yoshi, you'll need to carve out a lot of your time for Smash and keeping up with the Yoshis in the Discord.