I understand what you mean now. I did have a really long comment detailing a lot of things and sharing ideas on why I can or don't think it's a good idea to change, implement, or update the way it's setup at the moment. Most of my worries comes from game performance and the hit it'll take if it's having to RNG and load dozens and dozens of dates every time the player progresses time instead of just 4. And the ease of navigation, how much more of a pain it is to the player if scrolling is added into the mix.
But long story short, the problem is the lack of feeling the impact of the grind itself. When you level, the dates level with you, and that makes the player feel stagnant. In typical adventure RPGs, you progress by physically moving into harder areas and terrain. In Sugar Service, you are limited by a city and even more restricting, the in-game sms page.
A probable solution I may have is a star progression system and a city zone area system. Each 'page' (these will act like areas or zones of the city) will have 4-5 date opponents. You can earn stars by taking them out successfully. Based on how much health you have left on success, will determine how many stars you earn (how well you did). You can gain 3 or 5 stars (still deciding on the idea). To progress to the next area of the city, you'll have to spend your stars you earned.
You are free to grind out and max out all the levels but you are also free to get by with the bare minimum needed. For example, in one area, if every opponent has the potential for 5 stars, and there are 4 of them (ascending in levels), you can earn a maximum of 20 stars per area but you'll only be required to spend say 12 stars to proceed to the next area, which then hosts the next 4 harder opponents. Leveling up then going back to easier levels to max out the stars you havent collected so you can unlock harder areas will add to the progression you're looking for.
This may be the way to solve this gripe you have with the RPG, card grinding and how they feel lackluster in progression.