For Ryu and Ken: use more st. HP/MK to stuff fireballs on start up
For Sagat: it’s kind of a shenanigan, but you can use mk/hk SBK to go through low Tiger Shots
In general:
Cr. Roundhouse is an awesome move for beating other normals. It hits low and mid and it’s vulnerable hitbox doesn’t extend on either start up or recovery, so you can at least trade with practically anything. Throw some of those out there when it seems like they’re trying to keep you at bay with normals.
Also, throw more fireballs at mid-range. You can get a back charge by holding back during two cr. mks or st. mps, or one cr. hk. Not having to worry about your fireballs makes it a lot easier for shotos to fend you off. I personally really like throwing an lp fireball and then chasing it in. If they fireball to stop it, you can st. hp their recovery. If they block, do some low/throw mixups. If they just start throwing a lot of fireballs to keep you from doing that, start doing more jump ins.
I have this theory for fighting fireball characters, boiling it down to rock, paper, scissors. There’s turtle, rushdown, and zone (in this case zoning with fireballs to maximum distance). Turtle is just standing there and seeing what you do, rushdown is when they jump at you, and zone is when they throw fireballs. Turtle beats rushdown, rushdown beats zone, and zone beats turtle. So, if they are throwing lots of fireballs, jump more. If they are just standing there watching you, throw fireballs and chase them in. If they are jumping at you a lot, either keep a down charge for upkicks or be ready to do some neutral jump moves.
You get about as much advantage for landing a jump in as they do for knocking you down with an SRK, so don’t be scared to just guess and go for it. Waiting until you see the fireball animation can mean you won’t make it there in time, like in the Sagat fight. You can also see that they aren’t throwing a fireball and just empty jump so SRKs whiff. You’ll eventually lose in a fireball war if you try to go all out on that, but if you can lure them into one, you can find their pattern and get a jump in on them. Then, if they get scared to throw fireballs, just chase yours in, make them block one or throw theirs late in reaction, and make them pay for it.
Or, of course, you could just find easier people to fight than Daigo and Justin Wong.