You're going to have a provide an explanation for the "bland" and "doesn't require any thought process at all" arguments.
The reason people aren't playing Colonial games anymore has nothing to do with the fact that skirm/goon is too strong or anything like that. It's simply because the maps have more resources now, allowing you to remain safely in your base for a longer period of time; rendering Colonial contain strategies rather weak, as the defender will have plenty of time to tech up to Fortress and break the contain.
And, as you may be aware, there are actually plenty of maps in the map pool that promote exactly the kind of play you desire (e.g. Cascade Range, Pampas Sierras, Bengal, and Klondike, to name a few), and yet no one seems to want to play on them. Why not? Maybe because the types of strategies these maps tend to promote are unfun and are arguably easier to perform, making it difficult for a skilled player to differentiate themselves from an unskilled player (the all-in type strategies you want so badly), and also because even though everyone claims to want change, they don't want to actually have to play differently or invest time into learning new styles of play.
The game would actually be a lot more diverse if you all didn't insist on playing on the exact same type of map with the exact same type of resources every single game, what a shocker :O
you literally dont have to think about the unit composition, the build order, the micro etc, because its the same build and the same style of micro using only 2 units(mostly), same macro, literally the same units even with different civs. Always involving tp stagecoach
Now if you want to also promote different styles of play on maps that would typically cater towards boomy playstyles for example, you could look at a simple change like changing the Fortress politician age time: something I've wanted to change for quite some time.
It currently takes longer to age to Fortress than it does to any other age (110 seconds vs 90 seconds), unless you fast age of course (40 seconds). The key to making Colonial play more viable while also keeping Fortress as a solid option, you'd have to either increase the politician reward (e.g. 6 skirm > 7 skirm), decrease the age time (110 seconds > 100 or 90 seconds), and/or increase the age time for the fast age politician (40 seconds > 45 or 50 seconds).
This would make choosing which politician you age with a lot more important, and also opens more windows for punishment while still giving players a chance to outplay their opponent (or follow them up to fortress if their timing fails!).
Note that this change also improves current non-meta civs (Japan, India, China, Aztec, for example), while potentially weakening those current meta civs (German, Dutch, Port, France, etc.), but only in those situations.
I've suggested this change in the past, but no one seems to agree with me sadly.
Now if you want to avoid people only using skirm/goon compositions in Fortress, that's going to be harder; you'd have to seriously cripple the skirmisher (reduce damage) or reduce it's micro-ability (e.g. 20 range > 18 range). Somehow I doubt many people would be happy with either of these changes. You could maybe make skirms 5c or 5f more expensive? I could see myself losing games because I only got 4 skirms out in early fortress instead of 5.
You could do things like making TCs cheaper! If TCs are viable then people may have to invest into units with higher siege (cannons, heavy infantry, etc.), or play more aggressively in fortress to deny said TCs, where certain unit compositions may be stronger than skirm/goon, since goons kinda need a decent mass to defend skirmishers effectively, which would be especially difficult to get if you're investing in a town center.
Although in all seriousness the TC probably isn't quite cheap enough to warrant that, yet.
you literally dont have to think about the unit composition, the build order, the micro etc, because its the same build and the same style of micro using only 2 units(mostly), same macro, literally the same units even with different civs. Always involving tp stagecoach.
Its not the "all-in-style" that im so desirable about, did i not mention age 2 vs age 3 timings etc, also long colonials?
cheaper tcs will just involve the 2 falcs so thats irrelevant, you wont make heavy infantry in age 3 because theyre useless anyway so that siege argument is invalid.
Reducing the micro ability of skirms is the last thing everyone wants, just want to make age 2 play more viable with both maps and how gs mentions that the meta is "naturally shifting" to a semi tp meta, when all the age 2 civs are being nerfed directly or indirectly by ep (otto russia iro sioux azzy india japan) and all those civs being indirectly being buffed by ep and also directly buffed, providing a larger gap between the civs,brits, ports, dutch, france, prepatch german, china, etc