I think part of the disconnect is that we need to go back to the question of "Why do we do science in space IRL?"
The mechanic to get points to unlock the science tree is extremely abstract, as others have noted, but some existing modes do a great job of tying in science and exploration to directly furthering mission goals. For example, SCANSat altimetry provides night-landing assistance via the minimap feature allowing you to see the ground height you are heading for (before getting surprised by teh short-range radar alt in the cockpit!). The resource scanner likewise gives important data on ore concentration to allow you to plan the landing site for your ISRU to be effective.
This direct link between a module's abilities, the exploration task required for it to function (scan height and elliptic path for height/biome mapping, polar orbit for stock ore scan), and the benefits to mission planning and future missions is far more rewarding than the abstract science point system.
I'd like to see a way to make the same link for some of the other instruments, because part of the problem is that we start out *already knowing* about the whole solar system and the properties of the planets. Imagine if you could have things like:
-No planets beyond Duna revealed until a space telescope is orbited.
-No altimetry info unless pressure sensor or radar alt sensor carried on craft. Planet has to be altitude-mapped to threshold percentage before craft can have that info without carrying sensors.
-No trajectory prediction in an new SOI without a Gravioli accelerometer
Each of these steps could be rewarded on first instance with science points BUT more importantly, they directly contribute to the ability of the player to succeed at that mission and future missions.
Similarly for other parts development, I'd love to see them tied to specific accomplishments, such as:
-Materials study in X different space environments -> unlocks Y part node
-Accumulated X days on crewed mission -> unlocks Y crew module
-Mystery goo in X different biomes -> unlocks Y crew/exploration/lifesupport-related tech node
-Sat comm constellation with X sats connected -> dish tech node
Is it still grindy? Potentially, but it's at least outcomes are more closely tied to actions. Changing the # required is an easy way to adjust the difficulty/grind factor.
I'm not sure if it'd be possible to break the tech tree down such that a node can be unlocked, but have part Y from that node is restricted till a mission goal is met, but that is something that could keep the objective a bit more intuitively inline with existing tech nodes (e.g. unlocking Space Exploration gets the ladders and wheels, but the hitchhiker crew modules require a mission goal - actually this might be able to be tied into how contracts check for part unlocks, if unlocking the node can then generate a mission contract that sets a 'first' milestone to enable that part?)
These can all still generate generic science points to fill in areas of the tech tree that might not have a mission goal/experiment that makes sense, but having mission objectives tied more closely to both unlocking the tech AND developing future mission abilities gives us a great reason to keep hauling science kit out to the deep black.