SE does not necessarily suck at space race... My poor result in this example game (1888 AD) made me consider what circumstances are pro-SE / pro-CE.
The strength of an SE is the ability to build infrastructure while under slavery. The strength of a CE is, well, cottages. They are really good, as eveyone has probably noticed
So, not to seem off topic (since this test is about Monarch with this specific map), I ran a test game as Gandhi / Prince / Marathon so I could get these points clear:
1. Territory. An SE should be able to "tame" territory much more effectively and later in the game (up to 1000 AD) since by growth/whipping new cities can be setup fast. Later than 1000 AD wars are iffy for an early space race.
2. Trading disabled since it depends on diplomacy/luck (the AI doesnt always research well enough to catch up with a space race player). On prince the AI research is next to useless.
3. Effective switching between research/infrastructure building. For a CE this is done by the research slider with Universal Suffrage, but with a SE one switches slavery / caste system. Hence Gandhi, allowing quick switching.
4. Micromanagement. An SE is much more micro-heavy (at least for me) than a CE. Hence marathon speed (yes this also allows quicker conquest, I know..)
With this setup and intensive micromanagement I got a space launch at 1556 AD, my personal best. So at least as far as I'm concerned I consider SE viable for space race.
Taking these observations to the map in question I would assume the best strategy is to use the military power of SE to capture as much territory as possible before ca 1000 AD.
This is of course hard at normal speed but since I think it is clear that the beaker increase in time per city of the CE is more greater, an SE player must leverage their early military potential to even the score.
Get biology as soon as possible (in my test game I got it ca 1120 AD, same turn as Taj Mahal). Use golden ages to grow and increase infrastructure and in between run caste system with aggressive allocation of specialists.
Bulbing is very powerful up to ca Biology/Physics. After that it only augments a strategy already in place and wont "save" ones game..