Ok, I do get that, as far as combat goes, strength and dexterity are competing for a lot of the same space. That said, it isn't ALL the same space.
The point of the game is that your DM is supposed to challenge you, so you may not be making a mistake if placed in a position where your best option does not have the highest chance of success. All classes and subclasses have strengths and weaknesses and all players do their best to plug or avoid the weaknesses. That's the game working as best it can. Smart monsters will try to catch you out and succeeding against the odds is part of the fun.
But in what situation is attempting a disarm your best action as a Rogue? Or a grapple? Sure, maybe you can come up with some situation where an enemy has the McGuffin and is running to a portal, and only the rogue has the speed to close the distance and tackle them to get the item, but they can't use sleight of hand, because of the size of the item.... but that isn't going to happen every adventure.
And what the things monsters are going to do? Grapple? Well, the rules allow you to use Dexterity to slip out of a grapple. And, even while grappled the rogue can still do most everything else in their kit. So, again, while it sounds very good and true to say that "everyone has strength and weaknesses" and you need to fortify those weaknesses because "smart monsters will try to catch you out" in practice... That doesn't show the whole picture. If the worst a low strength causes is you needing more special equipment and to occasionally get caught in melee with a monster, it is far far less dangerous than the myriad of dangers you can face from lower wisdom for example.
And meanwhile, the benefit that was being discussed? It was about dynamic movement through the battlefield. Not exactly something that we really need to prevent or give a high cost to attaining.
I am struggling to understand your claim that rogues aren't mobile enough though. They can use their bonus action to dash, and new weapon masteries make that even easier if you are a two weapon build. Swashbucklers can bounce in and out of melee. Thieves can climb quickly. Any Rogue can put expertise in movement skills. Arcane tricksters can cast Jump, levitate, fly, or misty step. If you don't have the right subclass, you can pick mobile, or athlete, possibly other feats. You can partner with a battlemaster fighter for various combos. You can partner with an ally with Sentinel for combos.
There are loads of ways to build your Rogue character. Is what you are concerned about just that you want to be able to do all those things without additional investment?
Okay, you are conflating multiple points here, and arguments from different people, then turning around with an accusation.
1) I never stated that Rogues are not Mobile enough. That was the position of another poster, with whom you are discussing.
1a) Their position is more specific than "not mobile enough". It is that they should not be penalized by the reality of the game, by making it harder to do what the archetype indicates they should do. That is jumping and climbing specifically. Bouncing in and out of melee has nothing to do with it. Casting spells has nothing to do with it. Partnering with people who have other abilities is a non-sequitor entirely.
2) MY point was that there is no problem in redesigning the movement rules, to allow for more dynamic movement. This is a potential solution to the problem that poster was speaking to, the difficulty in movement using jumping and climbing.
2a) I made this point because YOU stated that you wanted people to not merely complain, but to offer solutions. However, your solutions were focused on "how do I make strength useful for rogues" which is not the complaint.
2b) To further my point, I mentioned that ALL DnD characters tend to be incredibly static. The most common thing I see a rogue do is stand 60 ft back with a ranged weapon and snipe the enemy repeatedly. Melee characters tend to stay in one place. Casters tend to barely move. This lack of dynamic movement is sometimes seen as a very boring part of DnD combat, and so fixing it while ALSO addressing the complaint of the other poster, could be seen as a good thing in and of itself.
3) This is NOT about wanting to do things without an investment. Fighters who invest heavily in strength are also static and barely interact with the world of DnD in a 3-dimensional manner. This is about offering a solution, after you demanded one, and showcasing that the solution to this idea that dex-archetypes have a hard time fulfilling parts of their archetype (archer in the trees, duelist swinging from chandeliers, a criminal climbing a tower) is not required to be "make dex characters also want a high strength score"