People complain about the Ranger due to comparing it to other combat classes. When you white-room sim all the classes, the Ranger comes out low because the two main class features they get at low level (Favored Enemy and Natural Explorer) do not help mechanically in combat, unlike almost all the other combat classes which get at least one.
But honestly... a player will usually only notice this discrepancy if they are really familiar with how all the classes play through personal experience, or the party consists of like 3 other major combat classes all of which are played by experienced, number-crunching players. But if you have your Ranger player, a Cleric, a Rogue, a Warlock, and a tanking Barbarian... I honestly doubt that the Ranger player will ever notice anything subpar about the class during combat. Especially come 2nd level and they start using Hunter's Mark to add an extra 1d6 damage on every attack they do. Even moreso when they hit 3rd and take the Hunter subclass. And if they are going Archery rather than melee... even moreso on top of that.
The complaints about the Beastmaster subclass? Yeah... the idea that from 1st to 4th level the Ranger itself doesn't ever attack because the Action is spent by the beast companion attacking is kinda lame. So I get it. But I have a Beastmaster Ranger in my current game and I just houseruled that provided the Ranger took a companion of CR 1/8 or lower (normally a BM gets CR 1/4)... then the Ranger and the companion would both be allowed to attack each round. Seeing as how the Beastmaster feature adds the Ranger's proficiency bonus to the companion's AC, attacks, damage, and proficient skills and saves... it ended up being a wonderful compromise and she's never had any complaints...
...especially considering that she as the Ranger pretty dominates all the scouting, travel, and outdoor parts of the game. With the number of people here on the boards that complain that Fighters get "nothing" for the Exploration and Social pillars of the game and it's only all about combat for them... we have here the absolute best class for continuous Exploration but yet people still think the class stinks.
If you want to use an alternate Ranger, sure, I wouldn't say anyone's wrong for suggesting it. But I also think the people who say that the Ranger as displayed in the Player's Handbook is untenable as an option are being rather hyperbolic.