Yes, but would you use Mega Beedrill over say Mega Scizor (for Bug-type), Mega Gengar (for Poison-type), or the other Megas for Pseudo Legendaries, Starters, or some of the other more popular Megas? Even in LGPE you still had the Mega Starters, Gengar, & Aerodactyl.
I think the Megas do need some fixing, specifically with how much stats are increased. The +100 BST isn't enough to help the Pokemon who didn't have that high of stats to start with catch-up. Not to mention a Pokemon who has a Mega you'd want to have it go Mega over holding a Life Orb or Choice Item. To start with I think they should make the stat increases percentage base instead of a flat number, I don't think we'd have such huge numbers as we have now so a bit more balanced and easier for the lower BST Pokemon to catch-up (especially with the right Ability). Also would get rid of the need to decrease a stat in order to increase another stat unless the decrease would benefit the Pokemon (like making a slow the Pokemon even slower to take advantage of Trick Room).
I disagree with the issue being the base stats.
Several Megas have very solid base stats, but a mediocre abilities. Most currently existing megas are OU/UU already, or viable in both tiers. I think the real issue is said Mega Evolutions not fixing a problem with the base pokemon, poor allocation of the stats, or a mixture of the two, alongside a mediocre ability.
Looking at the Mega Evolutions currently tiered under UU, we have our selection of:
Abomasnow: Its Mega takes a slow, frailish Ice-Type with even worse than usual typing; and turns it into an even slower Ice-Type with worse than usual typing with added bulk and offenses. The only real difference between pre and post-mega Abomasnow is that Abomasnow can take neutral hits better and hits slightly harder than an Abomasnow with a Life Orb. This combined with a lack of reliable recovery and an unchanged ability makes for a pokemon that constantly has to take hits before dishing them out, and simply cannot keep up. If it had gotten instead, a unique weather that didn't hinder one of its only recovery moves(synthesis) or a speed boosting ability instead of going down the typical immovable glacier path it might be better.
Ampharos: Ampharos' Mega Evolution is similar to Abomasnow in that it takes speed and adds defenses/offenses, though it also adds the useful Dragon Typing to go along with it. This time however some of that lost speed is for whatever reason donated to Ampharos' Attack for it to use some of its near nonexistent physical coverage(Ampharos has a grand total of 8 physical moves with a BP over 60 that are not normal type moves, 2 of those are STAB, and 2 of them are Focus Punch and Dynamic Punch). Once again, a lack of recovery makes for a slow moving (though significantly harder hitting) Pokemon that has to take hits before responding. Mold Breaker is the real punch in the stomach for Mega Ampharos, as it does nearly nothing for it at all(at the very minimum, Snow Warning gives Abomasnow perfect blizzard accuracy and chip damage), as opposed to an ability that compliments its new bulk or sky-high attack.
Banette: Banette's Mega dumps most of its stats into Attack, then spreads the rest semi-evenly to the other stats. This results in a hard hitting, slow Pokemon with no appreciable bulk. Prankster is an amazing ability, and is essentially the only saving grace Mega Banette has, allowing it to spread status and taunt foes with impunity. Unfortunately, the lack of speed and bulk prevent it from being anything other than a frail wallbreaker with support capabilities. Not putting stats into its frankly useless special attack and shaving off some of its defenses would have resulted in a faster Pokemon capable of handling itself just fine offensively while being able to patch up its poor defense with priority Wil O Wisp.
Blastoise: Mega Blastoise is a slow(noticing a pattern here?), hard-hitting water type with solid defenses and good coverage. It's faster than the previously mentioned Megas, but is also held back by a lack of recovery. Once again, stats have been dumped into an attack stat that it will never be using as a special attacker instead of putting it into speed or its defenses. Otherwise decent.
Glalie: Glalie is just simply an awful pokemon and Mega Glalie is only slightly better. Instead of pumping the Attack stat it wants to use with Refrigerate(Glalie does not get any special normal moves over 60 BP other than Hyper Beam) or even its speed; a whole 40 points were dumped into its comparatively useless special attack. Mega Glalie would almost absolutely be better with 20 more points in speed and attack.
Audino: Audino is the victim of being stuck with a doubles-specific ability when it would have really appreciated being allowed to have Regenerator, or really any other ability that was actually useful. 106/126/126 defenses are quite good when backed up by a pretty solid typing, and even base 80 sp. attack is usable, but once again, it's slow and effectively has no ability to use in a game where most battles are 1v1.