The Old World - update (?)

Things like cavalry & smaller units were much more viable in earlier editions than 8th, which makes the armies easier to collect.

5th edition has the herohammer tag, but tbh it´s an unfair tag, characters back then were no better than they are in 8th edition, there was no unbreakable daemon princes with incredible saves, no unkillable lords. Basic champions got to have magic items, which helped a lot vs overpwered characters, Black gem of Gnar locked a character in time, heart of woe exploded when you got killed, Black Amulet rebound wounds, Talisman of Ravensdark made creatures with flying useless, every army had access to these items, so people couldn´t just take a tooled up dragon rider lord & hope to win.
Magic was tougher to cast, you could have as many dispel scrolls as you wanted.
Yes characters could dominate if you didn´t take actions against it, but nowhere near what they can do in 8th edition.
Having said that, 5th edition had its flaws as well, I wouldn´t want a game just like that, I want something from each edition that could help make a perfect edition, a fun edition with balance (it should still have those oh shit moments), but not a tournament game like chess, 9th age or KoW.

Step-up is part of the problem, as is hordes & steadfast.
Personally I would like a mix between 6th & 8th.
Chargers strike first, casulties are allowed to strike back but suffer a small (-1) to hit penalty as well as having outnumbering bonus back again instead of steadfast (but count actual models & not unit strength, this gives infantry the edge, or change steadfast so a flanking force removes it).

Even in a smaller scale game there is nothing stopping you putting massive regiments down. You just play higher points

Each to his own I guess, I like the sight of a horde, I don´t like the rules of a horde, why would you be able to strike with an extra rank because your unit is deployed wider, I would rather see something that maybe negates the rankbonus of the enemy (the fluff could be that they´re about to be surrounded by the enemy horde). However I was never a fan of including supporting attacks in the first place (step-up should have a penalty, only spearlike weapons should add support attacks), It´s these rules that make large units a must in 8th edition....

That is not my experience, but of course this may differ depending on person. In 5th some of the special characters and weapon combinations were just wrong. Kragg the Grim with his S10 D6 wound hammer just smashing anything he touched. The hydra sword weilding vampire lords (that's 4xD6 s7 attacks for you younger folks) etc. Most regiments on the field were just decorations, when facing such odds. Of course me and my gaming friends were very young. Buidling the most OP combos was a natural part of the game for us back then. Only much later did I find out that a more gentelmanly approach provides a more enjoyable experience for all. However I feel 5th encouraged these silly builds more than other editions. 

As for specific 8th ed stuff, the horde rule I could do without. I preffer multiple moving pieces to fewer, suped-up deathstars. Alternatively, tweaking it is also an option. From what I recall in 9th age hordes do not provide rank bonus, which I think is an elegant solution and gives the smaller units a purpose.

I am in favor of the 'step-up' rule and support attacks. Nothing more annoying than watching your troops getting cut down every turn by a higher initiative opponent, without  being able to respond. Recently had a 6th ed game where my 20 strong greatsword block did not have a chance to swing a single time over 4 rounds of combat. Just reminded me of poorly infantry faired against cavalry and monsters back then. 

Each edition has its weaknesses, but I feel that 8th with a little bit of tweaking could really shine.