Hi,
You're comparing apples and oranges.
First of all you're comparing 1 country to a diverse group around 12 countries. Ukraine is not in Southeast Europe by any definition.
Kosovo, Macedonia, Serbia, Bosnia Herzegovina, Albania are much less touristy than Morocco. Croatia, Greece, Cyprus, Bulgaria is about as touristy as Morocco. It all depends of course on the exact location and the season.
Talking about the season, which are these 3 months?
3 months is a lot in Morocco, but very short for the entire Southeast Europe.
Morocco and Southeast Europe don't combine well with each other. I mean logistically it couldn't be easier to fly between them(cheap flights from Morocco to Istanbul by Air Arabia), but they have little to do with each other, totally different places. On the other hand the Iberian Peninsula has a lot in common with Morocco, history, culture and it makes sense to see them on the same trip.
I'd choose either some countries of Southeast Europe(not all of them!) OR do Morocco and Spain(and maybe Portugal).
The time of the year could be also decisive. Morocco and Southern Spain are usually fine even in winter(unless you want beach activities), spring and autumn would be ideal, while Southeast Europe is best from April to October.