i think its just you. sure, it took a bit longer this time around with the 63 characters that you need to unlock, but the difficulty felt around the same. some i was able to KO in under 20 seconds, but others did admittedly put up a fight. however, i was able to unlock all of them, only needing to rematch about 8 - 10 of them.
but you are correct in your assumption - Melee was and still is one of the most precise fighting games ever made, but it done on accident due to low development time. people fell in love with its quick gameplay and broken mechanics, so Brawl was made to slow down and soften the gameplay to make it more accessible to new players. Smash 4 was then meant to fall somewhere in the middle to unite both casual and competitive fans under one roof, but it didnt quite work. so the purpose of Ultimate was meant to truly unite all fans by bringing back all the fighters and fine-tuning the game to work for any play style. so yes, it is geared more towards the competitive crowd, and as a result it can be more difficult.