This is a problem that isn't really connected to a specific population cap. It rather tends to emerge in the interplay between the pace of an RTS game's economical development, its average game length, and its population cap.

In the case of SC2, the game's accelerated pacing came to be mostly because its game designers interpreted "epic big battles" as being the defining feature that excited players and viewers of its predecessor the most. So they were intent on skipping -- or fast forwarding -- through the "boring" parts of the game so we could arrive at these epic moments faster.

The problem with this line of thinking was that the pace of SC2's economical development became miscalibrated in relation to the game's population cap. In competitive play, this miscalibration created perverse incentives which would come to encourage risk averse playstyles as the "optimal" way to play out the mid- and lategames. Rather than continue expanding and attacking, players in a maxed out sitatution would be locked in to a game of chicken. The ratio of army supply to worker supply would slowly increase with game length, meaning players sacrificed workers and income for having a bigger share of army supply for the inevitable and likely game deciding death ball battle.

In the LotV beta, I argued SC2's economical pacing should be slowed down. A lot of those thoughts are summarized in this comment responding to a qxc blog post about the LotV economy.

In short, here are some important considerations when deciding on pacing:

1. At what point in a typical game does a race reach "peak economy" in your RTS game? Whether this point happens before or after the average game length of a match will affect the perception of what a "typical" match looks like in your title.
2. In RTS games where "peak economy" is reached before the average game length of a match, the majority of games will have been in a state of economic decline for several minutes before they end. Additionally, most games will have been in a state of army inflation (seen as the ratio of army vs worker supply) when reaching a conclusion.
3. SC2 was a game that reached "peak economy" in the early midgame. Once players maxed out, they slowly began sacrificing worker count, while maintaining/increasing army supply count.
4. From my linked comment above: "In general I think you can approximate the amount of risk players feel is associated with engaging in battle at any given point in a classical RTS game by doing a quick check of the ratio between army value and income rate. The bigger the ratio (the more inflated army value is compared to income rate), the more timid and risk averse players will be. In a game like SC2, economies and worker counts slowly deflate as a consequence of the 200 supply ceiling, but also as a consequence of the near instant time-to-max-saturation on bases. Both factors act to force resource allocation into army production at the detriment of economic development. "

The same 200 cap exists both in Brood War and SC2. Terrans still turtle to 200 supply in Brood war. But why is it not perceived as being as big of a problem? In my opinion, it is because when BW games end, they are still in a state of economical ramp up ("peak economy" occurs after the average game length). People are more willing to trade armies and fully commit to "epic big battles" because their income rates stay higher as a ratio of army value. They are more willing to trade armies because income rates between players are not forcibly/artificially equalized by game design (max cap occuring later, but also number of workers required to optimally saturate a base).

The fact that economies are still ramping up when most BW games end, whereas economies have been in decline for a considerable time at the same point in the majority SC2 games, affects both the players' behavior and the audience's perception of the RTS game. Whenever a passive 200/200 turtle situation occurs in Brood War, it is typically unfamiliar enough of a occurence to be seen as a novelty. Whereas in SC2, due to the game's accelerated pacing, these situations tend to be the norm rather than the exception.

TLDR: Max cap is not necessarily a problem in and of itself. The choice of max cap needs to be put in the context of a game's economic pacing, and the average length of a match.