Would the game have been better off without SI?

I can see what you're saying. If SI wasn't a thing, people like Takumi would still be king. I do like that SI allows you to give other units a chance (you can put great skills on a lower tier unit). There are cookie cutter builds and in the end it comes down to merges and IVs but I am kind of glad that SI came to the game. Of course it does mean you can make your units broken but to an extent they are unique

Hector, Ryouma, Azura, Nino, Linde, and Takumi were still the top tier pre-inheritance and every high end team had them, possibly in multiples. Reinhardt became more popular as a method of countering all the popular red heroes and honestly, mine has nothing inherited yet, just 5-star and a +atk boon and he still slaughters most things regardless.

You may think it was better before but it really wasn't. It's the same exact concept of 'this is the best set of units, everyone uses them now' just a slightly altered list of said units.

skill inheritance actually made a bunch of only middle tier units become much better. Yea the top guys were still on top but that's to be expected. Technically inheritance is what gave us the ability to have more heroes be decent.

Quadsuna
Raven Sophia
Swordbreaker Nowi
Brave Axe Cherche
Brash Assault Lyn
Quad Hana
Quad/Brave Raven
Quadelia
breaker builds
the potential to make a decent unit out of your favorite heroes that might have been bad before

The game honestly gained a lot more variety imo thanks to inheritance compared to before. Before if you met a whale arena team with 3 Hectors and an Azura you cried and tried again. Now that's very rare and being able to counter and kill Hector is much easier these days with axe breakers, TA, gem weapons, fire/windsweep weapons/skills, etc that it forces the meta to shift.

Right now for example, the meta is blue mage dominated. However that's because everyone started with their favorite red heroes like Marth, Roy, Lucina, Ryouma, etc. all were weak vs Reinhardt (even pre-inheritance) and Linde or other strong blue heroes. That's why more and more people shifted and now more teams are being forced to run more greens to counter this popularity of blue mages and soon the meta will shift once again to green heavy teams as a result and so on.

tl;dr Skill Inheritance makes the whole game better and permits a shifting meta to even exist.

I'll tell you what this game was like pre-SI:

Hector, takumi.

That's it. That's all the game was.

Without SI i would say is more fair play but still there would be some Heroes still just useless. Was Hector actually a strong hero befor SI? I must actually say no. Without SI Hector will just die no mighty Vantage no nuke ability with Bonefire. Short said rip Hectors players are way more experience.

Dunno actually don`t know if Horse Emblem would be that weak without SI. Reinhardt and Olwen would be actually still strong with example Gunther thx to Hone Attack or Olivia normal hone. Players just saw in him first no potential then later with buffs test they actually saw hey he just murder everything thx to brave weapons effect. Problem rather was not many player had him with +atk back when SI was not a thing.

Think is actually not SI the problem if a Hero was to weak it was rather the stats of the Heroes.

No. SI made the game a lot more dynamic, in my opinion. But I wouldn't mind trying occasional throwback event where SI isn't applied.

Meta without SI => Ike, Linde, Takumi, Hector. Even less variety ...